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	$39.30	13.402%	$44.567	$44.57	$44.55	$44.60
Purchase #2	$144.73	4.571%	$151.3456	$151.35	$151.35	$151.30
Purchase #3	$59.83	9.366%	$65.4337	$65.43	$65.45	$65.40
Purchase #4	$34.74	3.680%	$36.0184	$36.02	$36.00	$36.00
Purchase #5	$191.88	13.679%	$218.1273	$218.13	$218.15	$218.10
Purchase #6	$193.90	3.500%	$200.6865	$200.69	$200.70	$200.70
Purchase #7	$74.65	5.201%	$78.5325	$78.53	$78.55	$78.50
7 purchase totals =	$739.03		$794.7110	$794.72	$794.75	$794.60