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	$110.73	12.414%	$124.476	$124.48	$124.50	$124.50
Purchase #2	$180.78	10.130%	$199.093	$199.09	$199.10	$199.10
Purchase #3	$77.51	10.835%	$85.9082	$85.91	$85.90	$85.90
Purchase #4	$232.46	13.516%	$263.8793	$263.88	$263.90	$263.90
Purchase #5	$88.51	12.337%	$99.4295	$99.43	$99.45	$99.40
Purchase #6	$57.52	6.276%	$61.13	$61.13	$61.15	$61.10
Purchase #7	$229.80	9.673%	$252.0286	$252.03	$252.05	$252.00
7 purchase totals =	$977.31		$1,085.9446	$1,085.95	$1,086.05	$1,085.90