Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$154.68	6.229%	$164.315	$164.32	$164.30	$164.30
Purchase #2	$101.48	10.288%	$111.9203	$111.92	$111.90	$111.90
Purchase #3	$246.60	12.356%	$277.0699	$277.07	$277.05	$277.10
Purchase #4	$155.70	4.593%	$162.8513	$162.85	$162.85	$162.90
Purchase #5	$214.84	5.581%	$226.8302	$226.83	$226.85	$226.80
Purchase #6	$103.85	11.201%	$115.4822	$115.48	$115.50	$115.50
Purchase #7	$119.86	3.234%	$123.7363	$123.74	$123.75	$123.70
7 purchase totals =	$1,097.01		$1,182.2052	$1,182.21	$1,182.20	$1,182.20