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	$221.85	12.737%	$250.107	$250.11	$250.10	$250.10
Purchase #2	$43.68	3.678%	$45.2866	$45.29	$45.30	$45.30
Purchase #3	$165.46	8.469%	$179.4728	$179.47	$179.45	$179.50
Purchase #4	$196.54	13.207%	$222.497	$222.50	$222.50	$222.50
Purchase #5	$149.59	13.801%	$170.2349	$170.23	$170.25	$170.20
Purchase #6	$6.75	6.449%	$7.1853	$7.19	$7.20	$7.20
Purchase #7	$221.28	6.758%	$236.2341	$236.23	$236.25	$236.20
7 purchase totals =	$1,005.15		$1,111.0177	$1,111.02	$1,111.05	$1,111.00