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	$147.89	3.406%	$152.9271	$152.93	$152.95	$152.90
Purchase #2	$208.81	13.675%	$237.3648	$237.36	$237.35	$237.40
Purchase #3	$229.46	8.653%	$249.3152	$249.32	$249.30	$249.30
Purchase #4	$43.75	3.500%	$45.2813	$45.28	$45.30	$45.30
Purchase #5	$72.29	8.790%	$78.6443	$78.64	$78.65	$78.60
Purchase #6	$94.73	12.383%	$106.4604	$106.46	$106.45	$106.50
Purchase #7	$84.73	11.252%	$94.2638	$94.26	$94.25	$94.30
7 purchase totals =	$881.66		$964.2569	$964.25	$964.25	$964.30