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	$172.56	10.410%	$190.5235	$190.52	$190.50	$190.50
Purchase #2	$130.76	8.542%	$141.9295	$141.93	$141.95	$141.90
Purchase #3	$235.42	4.704%	$246.4942	$246.49	$246.50	$246.50
Purchase #4	$215.90	8.145%	$233.4851	$233.49	$233.50	$233.50
Purchase #5	$111.39	12.673%	$125.5065	$125.51	$125.50	$125.50
Purchase #6	$238.95	7.215%	$256.1902	$256.19	$256.20	$256.20
Purchase #7	$141.33	7.384%	$151.7658	$151.77	$151.75	$151.80
7 purchase totals =	$1,246.31		$1,345.8948	$1,345.90	$1,345.90	$1,345.90