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	$100.59	7.820%	$108.4561	$108.46	$108.45	$108.50
Purchase #2	$196.41	11.315%	$218.6338	$218.63	$218.65	$218.60
Purchase #3	$39.25	9.197%	$42.8598	$42.86	$42.85	$42.90
Purchase #4	$228.79	6.368%	$243.3593	$243.36	$243.35	$243.40
Purchase #5	$9.67	12.114%	$10.8414	$10.84	$10.85	$10.80
Purchase #6	$130.35	10.392%	$143.896	$143.90	$143.90	$143.90
Purchase #7	$36.60	13.436%	$41.5176	$41.52	$41.50	$41.50
7 purchase totals =	$741.66		$809.5640	$809.57	$809.55	$809.60