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	$99.29	9.436%	$108.659	$108.66	$108.65	$108.70
Purchase #2	$164.70	5.870%	$174.3679	$174.37	$174.35	$174.40
Purchase #3	$200.68	11.484%	$223.7261	$223.73	$223.75	$223.70
Purchase #4	$225.53	12.562%	$253.8611	$253.86	$253.85	$253.90
Purchase #5	$189.45	3.690%	$196.4407	$196.44	$196.45	$196.40
Purchase #6	$21.47	13.672%	$24.4054	$24.41	$24.40	$24.40
Purchase #7	$59.26	12.712%	$66.7931	$66.79	$66.80	$66.80
7 purchase totals =	$960.38		$1,048.2533	$1,048.26	$1,048.25	$1,048.30