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	$131.44	11.317%	$146.3151	$146.32	$146.30	$146.30
Purchase #2	$62.69	11.817%	$70.0981	$70.10	$70.10	$70.10
Purchase #3	$87.95	8.525%	$95.4477	$95.45	$95.45	$95.40
Purchase #4	$118.71	7.308%	$127.3853	$127.39	$127.40	$127.40
Purchase #5	$86.54	8.113%	$93.561	$93.56	$93.55	$93.60
Purchase #6	$229.64	12.659%	$258.7101	$258.71	$258.70	$258.70
Purchase #7	$233.61	7.244%	$250.5327	$250.53	$250.55	$250.50
7 purchase totals =	$950.58		$1,042.0500	$1,042.06	$1,042.05	$1,042.00