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	$134.73	13.362%	$152.7326	$152.73	$152.75	$152.70
Purchase #2	$219.73	13.519%	$249.4353	$249.44	$249.45	$249.40
Purchase #3	$34.70	7.620%	$37.3441	$37.34	$37.35	$37.30
Purchase #4	$57.72	12.152%	$64.7341	$64.73	$64.75	$64.70
Purchase #5	$164.80	11.225%	$183.2988	$183.30	$183.30	$183.30
Purchase #6	$155.48	11.754%	$173.7551	$173.76	$173.75	$173.80
Purchase #7	$196.88	12.830%	$222.1397	$222.14	$222.15	$222.10
7 purchase totals =	$964.04		$1,083.4397	$1,083.44	$1,083.50	$1,083.30