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	$73.58	10.715%	$81.4641	$81.46	$81.45	$81.50
Purchase #2	$129.95	13.502%	$147.4958	$147.50	$147.50	$147.50
Purchase #3	$247.78	4.776%	$259.614	$259.61	$259.60	$259.60
Purchase #4	$40.65	11.362%	$45.2687	$45.27	$45.25	$45.30
Purchase #5	$39.59	4.581%	$41.4036	$41.40	$41.40	$41.40
Purchase #6	$67.59	7.674%	$72.7769	$72.78	$72.80	$72.80
Purchase #7	$230.59	8.412%	$249.9872	$249.99	$250.00	$250.00
7 purchase totals =	$829.73		$898.0103	$898.01	$898.00	$898.10