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	$223.57	13.409%	$253.5485	$253.55	$253.55	$253.50
Purchase #2	$154.94	11.809%	$173.2369	$173.24	$173.25	$173.20
Purchase #3	$237.42	4.181%	$247.3465	$247.35	$247.35	$247.30
Purchase #4	$45.89	13.441%	$52.0581	$52.06	$52.05	$52.10
Purchase #5	$230.96	5.191%	$242.9491	$242.95	$242.95	$242.90
Purchase #6	$168.78	12.165%	$189.3121	$189.31	$189.30	$189.30
Purchase #7	$59.36	13.138%	$67.1587	$67.16	$67.15	$67.20
7 purchase totals =	$1,120.92		$1,225.6099	$1,225.62	$1,225.60	$1,225.50