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	$89.54	10.438%	$98.8862	$98.89	$98.90	$98.90
Purchase #2	$209.82	7.285%	$225.1054	$225.11	$225.10	$225.10
Purchase #3	$50.72	13.758%	$57.6981	$57.70	$57.70	$57.70
Purchase #4	$56.37	4.727%	$59.0346	$59.03	$59.05	$59.00
Purchase #5	$179.88	10.373%	$198.539	$198.54	$198.55	$198.50
Purchase #6	$14.73	7.325%	$15.809	$15.81	$15.80	$15.80
Purchase #7	$186.43	7.416%	$200.2556	$200.26	$200.25	$200.30
7 purchase totals =	$787.49		$855.3279	$855.34	$855.35	$855.30