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	$178.85	10.229%	$197.1446	$197.14	$197.15	$197.10
Purchase #2	$200.64	13.375%	$227.4756	$227.48	$227.50	$227.50
Purchase #3	$219.34	7.528%	$235.8519	$235.85	$235.85	$235.90
Purchase #4	$74.41	5.164%	$78.2525	$78.25	$78.25	$78.30
Purchase #5	$197.32	4.506%	$206.2112	$206.21	$206.20	$206.20
Purchase #6	$233.78	7.149%	$250.4929	$250.49	$250.50	$250.50
Purchase #7	$151.67	10.443%	$167.5089	$167.51	$167.50	$167.50
7 purchase totals =	$1,256.01		$1,362.9376	$1,362.93	$1,362.95	$1,363.00