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	$98.63	13.213%	$111.662	$111.66	$111.65	$111.70
Purchase #2	$105.42	6.573%	$112.3493	$112.35	$112.35	$112.30
Purchase #3	$33.85	10.309%	$37.3396	$37.34	$37.35	$37.30
Purchase #4	$153.78	10.449%	$169.8485	$169.85	$169.85	$169.80
Purchase #5	$36.81	5.155%	$38.7076	$38.71	$38.70	$38.70
Purchase #6	$93.96	8.436%	$101.8865	$101.89	$101.90	$101.90
Purchase #7	$206.51	7.131%	$221.2362	$221.24	$221.25	$221.20
7 purchase totals =	$728.96		$793.0297	$793.04	$793.05	$792.90