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	$216.66	7.468%	$232.8402	$232.84	$232.85	$232.80
Purchase #2	$178.78	3.874%	$185.7059	$185.71	$185.70	$185.70
Purchase #3	$79.36	12.631%	$89.384	$89.38	$89.40	$89.40
Purchase #4	$237.51	5.478%	$250.5208	$250.52	$250.50	$250.50
Purchase #5	$118.61	4.607%	$124.0744	$124.07	$124.05	$124.10
Purchase #6	$237.75	5.535%	$250.9095	$250.91	$250.90	$250.90
Purchase #7	$16.34	10.551%	$18.064	$18.06	$18.05	$18.10
7 purchase totals =	$1,085.01		$1,151.4988	$1,151.49	$1,151.45	$1,151.50