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	$69.50	6.668%	$74.1343	$74.13	$74.15	$74.10
Purchase #2	$56.79	8.104%	$61.3923	$61.39	$61.40	$61.40
Purchase #3	$41.50	11.514%	$46.2783	$46.28	$46.30	$46.30
Purchase #4	$147.70	5.263%	$155.4735	$155.47	$155.45	$155.50
Purchase #5	$250.59	9.547%	$274.5138	$274.51	$274.50	$274.50
Purchase #6	$221.79	3.353%	$229.2266	$229.23	$229.25	$229.20
Purchase #7	$240.27	9.194%	$262.3604	$262.36	$262.35	$262.40
7 purchase totals =	$1,028.14		$1,103.3792	$1,103.37	$1,103.40	$1,103.40