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	$153.69	13.386%	$174.2629	$174.26	$174.25	$174.30
Purchase #2	$170.59	5.400%	$179.8019	$179.80	$179.80	$179.80
Purchase #3	$230.91	10.260%	$254.6014	$254.60	$254.60	$254.60
Purchase #4	$237.89	4.628%	$248.8995	$248.90	$248.90	$248.90
Purchase #5	$90.91	7.464%	$97.6955	$97.70	$97.70	$97.70
Purchase #6	$39.92	11.572%	$44.5395	$44.54	$44.55	$44.50
Purchase #7	$55.75	10.726%	$61.7297	$61.73	$61.75	$61.70
7 purchase totals =	$979.66		$1,061.5304	$1,061.53	$1,061.55	$1,061.50