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	$174.48	9.638%	$191.2964	$191.30	$191.30	$191.30
Purchase #2	$147.54	3.249%	$152.3336	$152.33	$152.35	$152.30
Purchase #3	$102.29	8.684%	$111.1729	$111.17	$111.15	$111.20
Purchase #4	$247.27	10.362%	$272.8921	$272.89	$272.90	$272.90
Purchase #5	$41.64	7.799%	$44.8875	$44.89	$44.90	$44.90
Purchase #6	$46.60	8.592%	$50.6039	$50.60	$50.60	$50.60
Purchase #7	$28.61	3.238%	$29.5364	$29.54	$29.55	$29.50
7 purchase totals =	$788.43		$852.7228	$852.72	$852.75	$852.70