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	$111.92	4.412%	$116.8579	$116.86	$116.85	$116.90
Purchase #2	$169.72	11.458%	$189.1665	$189.17	$189.15	$189.20
Purchase #3	$48.87	10.333%	$53.9197	$53.92	$53.90	$53.90
Purchase #4	$163.34	7.374%	$175.3847	$175.38	$175.40	$175.40
Purchase #5	$62.79	4.179%	$65.414	$65.41	$65.40	$65.40
Purchase #6	$33.34	13.670%	$37.8976	$37.90	$37.90	$37.90
Purchase #7	$203.52	8.124%	$220.054	$220.05	$220.05	$220.10
7 purchase totals =	$793.50		$858.6944	$858.69	$858.65	$858.80