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	$31.41	3.685%	$32.5675	$32.57	$32.55	$32.60
Purchase #2	$191.71	11.177%	$213.1374	$213.14	$213.15	$213.10
Purchase #3	$93.31	7.717%	$100.5107	$100.51	$100.50	$100.50
Purchase #4	$199.70	8.764%	$217.2017	$217.20	$217.20	$217.20
Purchase #5	$36.48	10.408%	$40.2768	$40.28	$40.30	$40.30
Purchase #6	$211.56	10.366%	$233.4903	$233.49	$233.50	$233.50
Purchase #7	$241.96	9.195%	$264.2082	$264.21	$264.20	$264.20
7 purchase totals =	$1,006.13		$1,101.3926	$1,101.40	$1,101.40	$1,101.40