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	$133.72	8.713%	$145.371	$145.37	$145.35	$145.40
Purchase #2	$39.46	9.841%	$43.3433	$43.34	$43.35	$43.30
Purchase #3	$53.43	11.371%	$59.5055	$59.51	$59.50	$59.50
Purchase #4	$110.88	12.148%	$124.3497	$124.35	$124.35	$124.30
Purchase #5	$24.52	10.871%	$27.1856	$27.19	$27.20	$27.20
Purchase #6	$132.92	3.635%	$137.7516	$137.75	$137.75	$137.80
Purchase #7	$173.62	9.154%	$189.5132	$189.51	$189.50	$189.50
7 purchase totals =	$668.55		$727.0199	$727.02	$727.00	$727.00