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	$136.95	11.585%	$152.8157	$152.82	$152.80	$152.80
Purchase #2	$162.29	6.564%	$172.9427	$172.94	$172.95	$172.90
Purchase #3	$51.73	7.603%	$55.663	$55.66	$55.65	$55.70
Purchase #4	$96.87	9.267%	$105.8469	$105.85	$105.85	$105.80
Purchase #5	$96.33	12.552%	$108.4213	$108.42	$108.40	$108.40
Purchase #6	$100.89	4.172%	$105.0991	$105.10	$105.10	$105.10
Purchase #7	$49.51	11.323%	$55.116	$55.12	$55.10	$55.10
7 purchase totals =	$694.57		$755.9047	$755.91	$755.85	$755.80