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	$226.80	10.518%	$250.6548	$250.65	$250.65	$250.70
Purchase #2	$89.42	6.635%	$95.353	$95.35	$95.35	$95.40
Purchase #3	$201.25	4.295%	$209.8937	$209.89	$209.90	$209.90
Purchase #4	$220.62	7.580%	$237.343	$237.34	$237.35	$237.30
Purchase #5	$50.42	8.162%	$54.5353	$54.54	$54.55	$54.50
Purchase #6	$162.98	7.162%	$174.6526	$174.65	$174.65	$174.70
Purchase #7	$134.46	11.642%	$150.1138	$150.11	$150.10	$150.10
7 purchase totals =	$1,085.95		$1,172.5462	$1,172.53	$1,172.55	$1,172.60