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	$62.74	8.857%	$68.2969	$68.30	$68.30	$68.30
Purchase #2	$53.54	10.600%	$59.2152	$59.22	$59.20	$59.20
Purchase #3	$114.63	8.490%	$124.3621	$124.36	$124.35	$124.40
Purchase #4	$76.41	9.281%	$83.5016	$83.50	$83.50	$83.50
Purchase #5	$224.39	13.871%	$255.5151	$255.52	$255.50	$255.50
Purchase #6	$116.32	12.215%	$130.5285	$130.53	$130.55	$130.50
Purchase #7	$165.25	5.500%	$174.3388	$174.34	$174.35	$174.30
7 purchase totals =	$813.28		$895.7582	$895.77	$895.75	$895.70