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	$108.91	9.871%	$119.6605	$119.66	$119.65	$119.70
Purchase #2	$70.25	3.138%	$72.4544	$72.45	$72.45	$72.50
Purchase #3	$114.37	9.217%	$124.9115	$124.91	$124.90	$124.90
Purchase #4	$204.68	3.803%	$212.464	$212.46	$212.45	$212.50
Purchase #5	$18.27	4.557%	$19.1026	$19.10	$19.10	$19.10
Purchase #6	$87.51	3.150%	$90.2666	$90.27	$90.25	$90.30
Purchase #7	$18.39	4.234%	$19.1686	$19.17	$19.15	$19.20
7 purchase totals =	$622.38		$658.0282	$658.02	$657.95	$658.20