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	$103.94	13.105%	$117.5613	$117.56	$117.55	$117.60
Purchase #2	$37.47	5.421%	$39.5012	$39.50	$39.50	$39.50
Purchase #3	$240.96	9.173%	$263.0633	$263.06	$263.05	$263.10
Purchase #4	$157.84	13.243%	$178.7428	$178.74	$178.75	$178.70
Purchase #5	$154.31	7.179%	$165.3879	$165.39	$165.40	$165.40
Purchase #6	$247.90	8.489%	$268.9442	$268.94	$268.95	$268.90
Purchase #7	$124.90	11.523%	$139.2922	$139.29	$139.30	$139.30
7 purchase totals =	$1,067.32		$1,172.4929	$1,172.48	$1,172.50	$1,172.50