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	$163.32	13.676%	$185.6556	$185.66	$185.65	$185.70
Purchase #2	$81.93	7.757%	$88.2853	$88.29	$88.30	$88.30
Purchase #3	$47.97	5.306%	$50.5153	$50.52	$50.50	$50.50
Purchase #4	$82.39	8.482%	$89.3783	$89.38	$89.40	$89.40
Purchase #5	$193.65	10.659%	$214.2912	$214.29	$214.30	$214.30
Purchase #6	$84.65	6.149%	$89.8551	$89.86	$89.85	$89.90
Purchase #7	$53.52	8.633%	$58.1404	$58.14	$58.15	$58.10
7 purchase totals =	$707.43		$776.1212	$776.14	$776.15	$776.20