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	$133.54	12.406%	$150.107	$150.11	$150.10	$150.10
Purchase #2	$231.52	4.643%	$242.2695	$242.27	$242.25	$242.30
Purchase #3	$119.25	5.576%	$125.8994	$125.90	$125.90	$125.90
Purchase #4	$37.54	7.830%	$40.4794	$40.48	$40.50	$40.50
Purchase #5	$211.43	3.686%	$219.2233	$219.22	$219.20	$219.20
Purchase #6	$127.96	9.122%	$139.6325	$139.63	$139.65	$139.60
Purchase #7	$161.58	6.365%	$171.8646	$171.86	$171.85	$171.90
7 purchase totals =	$1,022.82		$1,089.4757	$1,089.47	$1,089.45	$1,089.50