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	$140.60	7.393%	$150.9946	$150.99	$151.00	$151.00
Purchase #2	$196.59	13.433%	$222.9979	$223.00	$223.00	$223.00
Purchase #3	$209.65	10.600%	$231.8729	$231.87	$231.85	$231.90
Purchase #4	$88.81	8.698%	$96.5347	$96.53	$96.55	$96.50
Purchase #5	$89.58	8.115%	$96.8494	$96.85	$96.85	$96.80
Purchase #6	$18.50	12.292%	$20.774	$20.77	$20.75	$20.80
Purchase #7	$195.38	13.731%	$222.2076	$222.21	$222.20	$222.20
7 purchase totals =	$939.11		$1,042.2311	$1,042.22	$1,042.20	$1,042.20