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	$102.50	8.379%	$111.0885	$111.09	$111.10	$111.10
Purchase #2	$192.31	12.449%	$216.2507	$216.25	$216.25	$216.30
Purchase #3	$14.91	13.305%	$16.8938	$16.89	$16.90	$16.90
Purchase #4	$5.76	11.746%	$6.4366	$6.44	$6.45	$6.40
Purchase #5	$105.71	6.624%	$112.7122	$112.71	$112.70	$112.70
Purchase #6	$150.62	10.539%	$166.4938	$166.49	$166.50	$166.50
Purchase #7	$206.75	11.800%	$231.1465	$231.15	$231.15	$231.10
7 purchase totals =	$778.56		$861.0221	$861.02	$861.05	$861.00