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	$243.98	8.824%	$265.5088	$265.51	$265.50	$265.50
Purchase #2	$183.65	11.529%	$204.823	$204.82	$204.80	$204.80
Purchase #3	$207.50	4.732%	$217.3189	$217.32	$217.30	$217.30
Purchase #4	$57.65	3.822%	$59.8534	$59.85	$59.85	$59.90
Purchase #5	$241.34	11.294%	$268.5969	$268.60	$268.60	$268.60
Purchase #6	$46.96	6.602%	$50.0603	$50.06	$50.05	$50.10
Purchase #7	$214.25	9.849%	$235.3515	$235.35	$235.35	$235.40
7 purchase totals =	$1,195.33		$1,301.5128	$1,301.51	$1,301.45	$1,301.60