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	$85.38	7.476%	$91.763	$91.76	$91.75	$91.80
Purchase #2	$26.41	10.293%	$29.1284	$29.13	$29.15	$29.10
Purchase #3	$171.55	9.495%	$187.8387	$187.84	$187.85	$187.80
Purchase #4	$48.64	11.650%	$54.3066	$54.31	$54.30	$54.30
Purchase #5	$106.36	5.847%	$112.5789	$112.58	$112.60	$112.60
Purchase #6	$62.94	7.185%	$67.4622	$67.46	$67.45	$67.50
Purchase #7	$230.40	8.181%	$249.249	$249.25	$249.25	$249.20
7 purchase totals =	$731.68		$792.3268	$792.33	$792.35	$792.30