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	$109.86	12.281%	$123.3519	$123.35	$123.35	$123.40
Purchase #2	$248.30	4.427%	$259.2922	$259.29	$259.30	$259.30
Purchase #3	$113.31	8.693%	$123.16	$123.16	$123.15	$123.20
Purchase #4	$165.28	13.477%	$187.5548	$187.55	$187.55	$187.60
Purchase #5	$87.78	4.597%	$91.8152	$91.82	$91.80	$91.80
Purchase #6	$155.69	4.359%	$162.4765	$162.48	$162.50	$162.50
Purchase #7	$84.88	13.229%	$96.1088	$96.11	$96.10	$96.10
7 purchase totals =	$965.10		$1,043.7594	$1,043.76	$1,043.75	$1,043.90