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	$191.72	10.723%	$212.2781	$212.28	$212.30	$212.30
Purchase #2	$64.43	3.560%	$66.7237	$66.72	$66.70	$66.70
Purchase #3	$227.71	5.306%	$239.7923	$239.79	$239.80	$239.80
Purchase #4	$178.42	10.317%	$196.8276	$196.83	$196.85	$196.80
Purchase #5	$93.42	7.336%	$100.2733	$100.27	$100.25	$100.30
Purchase #6	$88.29	7.282%	$94.7193	$94.72	$94.70	$94.70
Purchase #7	$174.89	12.251%	$196.3158	$196.32	$196.30	$196.30
7 purchase totals =	$1,018.88		$1,106.9301	$1,106.93	$1,106.90	$1,106.90