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	$238.45	12.188%	$267.5123	$267.51	$267.50	$267.50
Purchase #2	$139.97	6.105%	$148.5152	$148.52	$148.50	$148.50
Purchase #3	$227.67	11.205%	$253.1804	$253.18	$253.20	$253.20
Purchase #4	$29.42	6.459%	$31.3202	$31.32	$31.30	$31.30
Purchase #5	$181.34	3.779%	$188.1928	$188.19	$188.20	$188.20
Purchase #6	$87.57	5.593%	$92.4678	$92.47	$92.45	$92.50
Purchase #7	$94.74	11.192%	$105.3433	$105.34	$105.35	$105.30
7 purchase totals =	$999.16		$1,086.5320	$1,086.53	$1,086.50	$1,086.50