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	$104.52	5.480%	$110.2477	$110.25	$110.25	$110.20
Purchase #2	$55.63	11.754%	$62.1688	$62.17	$62.15	$62.20
Purchase #3	$209.85	5.845%	$222.1157	$222.12	$222.10	$222.10
Purchase #4	$205.66	11.727%	$229.7777	$229.78	$229.80	$229.80
Purchase #5	$133.30	13.671%	$151.5234	$151.52	$151.50	$151.50
Purchase #6	$166.78	13.549%	$189.377	$189.38	$189.40	$189.40
Purchase #7	$111.78	5.791%	$118.2532	$118.25	$118.25	$118.30
7 purchase totals =	$987.52		$1,083.4635	$1,083.47	$1,083.45	$1,083.50