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	$67.44	10.685%	$74.646	$74.65	$74.65	$74.60
Purchase #2	$48.64	9.616%	$53.3172	$53.32	$53.30	$53.30
Purchase #3	$228.33	11.764%	$255.1907	$255.19	$255.20	$255.20
Purchase #4	$183.76	4.249%	$191.568	$191.57	$191.55	$191.60
Purchase #5	$243.26	4.179%	$253.4258	$253.43	$253.45	$253.40
Purchase #6	$94.42	8.450%	$102.3985	$102.40	$102.40	$102.40
Purchase #7	$211.55	5.126%	$222.3941	$222.39	$222.40	$222.40
7 purchase totals =	$1,077.40		$1,152.9403	$1,152.95	$1,152.95	$1,152.90