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	$7.96	12.317%	$8.9404	$8.94	$8.95	$8.90
Purchase #2	$209.89	4.600%	$219.5449	$219.54	$219.55	$219.50
Purchase #3	$56.59	4.869%	$59.3454	$59.35	$59.35	$59.30
Purchase #4	$150.72	7.418%	$161.9004	$161.90	$161.90	$161.90
Purchase #5	$36.61	13.188%	$41.4381	$41.44	$41.45	$41.40
Purchase #6	$46.26	9.530%	$50.6686	$50.67	$50.65	$50.70
Purchase #7	$163.69	5.647%	$172.9336	$172.93	$172.95	$172.90
7 purchase totals =	$671.72		$714.7714	$714.77	$714.80	$714.60