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	$183.48	11.650%	$204.8554	$204.86	$204.85	$204.90
Purchase #2	$90.55	12.434%	$101.809	$101.81	$101.80	$101.80
Purchase #3	$231.93	10.103%	$255.3619	$255.36	$255.35	$255.40
Purchase #4	$186.27	4.423%	$194.5087	$194.51	$194.50	$194.50
Purchase #5	$39.64	6.599%	$42.2558	$42.26	$42.25	$42.30
Purchase #6	$221.53	10.360%	$244.4805	$244.48	$244.50	$244.50
Purchase #7	$250.72	5.479%	$264.4569	$264.46	$264.45	$264.50
7 purchase totals =	$1,204.12		$1,307.7282	$1,307.74	$1,307.70	$1,307.90