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	$213.60	6.458%	$227.3943	$227.39	$227.40	$227.40
Purchase #2	$176.95	10.388%	$195.3316	$195.33	$195.35	$195.30
Purchase #3	$31.76	5.633%	$33.549	$33.55	$33.55	$33.50
Purchase #4	$53.36	7.717%	$57.4778	$57.48	$57.50	$57.50
Purchase #5	$143.75	4.413%	$150.0937	$150.09	$150.10	$150.10
Purchase #6	$169.68	13.678%	$192.8888	$192.89	$192.90	$192.90
Purchase #7	$184.58	11.136%	$205.1348	$205.13	$205.15	$205.10
7 purchase totals =	$973.68		$1,061.8700	$1,061.86	$1,061.95	$1,061.80