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	$179.68	9.486%	$196.7244	$196.72	$196.70	$196.70
Purchase #2	$108.89	12.464%	$122.462	$122.46	$122.45	$122.50
Purchase #3	$35.26	6.317%	$37.4874	$37.49	$37.50	$37.50
Purchase #4	$150.42	11.398%	$167.5649	$167.56	$167.55	$167.60
Purchase #5	$53.64	6.670%	$57.2178	$57.22	$57.20	$57.20
Purchase #6	$140.73	8.172%	$152.2305	$152.23	$152.25	$152.20
Purchase #7	$61.71	6.156%	$65.5089	$65.51	$65.50	$65.50
7 purchase totals =	$730.33		$799.1959	$799.19	$799.15	$799.20