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	$188.33	13.843%	$214.4005	$214.40	$214.40	$214.40
Purchase #2	$67.28	4.810%	$70.5162	$70.52	$70.50	$70.50
Purchase #3	$42.89	5.263%	$45.1473	$45.15	$45.15	$45.10
Purchase #4	$42.43	11.150%	$47.1609	$47.16	$47.15	$47.20
Purchase #5	$165.77	5.619%	$175.0846	$175.08	$175.10	$175.10
Purchase #6	$182.33	4.788%	$191.06	$191.06	$191.05	$191.10
Purchase #7	$161.48	11.805%	$180.5427	$180.54	$180.55	$180.50
7 purchase totals =	$850.51		$923.9122	$923.91	$923.90	$923.90