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	$232.83	7.699%	$250.7556	$250.76	$250.75	$250.80
Purchase #2	$238.85	10.566%	$264.0869	$264.09	$264.10	$264.10
Purchase #3	$10.33	12.869%	$11.6594	$11.66	$11.65	$11.70
Purchase #4	$225.87	11.520%	$251.8902	$251.89	$251.90	$251.90
Purchase #5	$71.49	3.380%	$73.9064	$73.91	$73.90	$73.90
Purchase #6	$210.28	5.436%	$221.7108	$221.71	$221.70	$221.70
Purchase #7	$61.46	9.669%	$67.4026	$67.40	$67.40	$67.40
7 purchase totals =	$1,051.11		$1,141.4119	$1,141.42	$1,141.40	$1,141.50