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	$222.71	12.367%	$250.2525	$250.25	$250.25	$250.30
Purchase #2	$79.89	7.503%	$85.8841	$85.88	$85.90	$85.90
Purchase #3	$143.50	10.129%	$158.0351	$158.04	$158.05	$158.00
Purchase #4	$225.38	12.406%	$253.3406	$253.34	$253.35	$253.30
Purchase #5	$192.49	11.642%	$214.8997	$214.90	$214.90	$214.90
Purchase #6	$152.57	4.413%	$159.3029	$159.30	$159.30	$159.30
Purchase #7	$110.93	3.504%	$114.817	$114.82	$114.80	$114.80
7 purchase totals =	$1,127.47		$1,236.5319	$1,236.53	$1,236.55	$1,236.50