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	$94.34	4.610%	$98.6891	$98.69	$98.70	$98.70
Purchase #2	$50.86	8.653%	$55.2609	$55.26	$55.25	$55.30
Purchase #3	$158.60	13.421%	$179.8857	$179.89	$179.90	$179.90
Purchase #4	$77.33	7.623%	$83.2249	$83.22	$83.20	$83.20
Purchase #5	$165.76	10.364%	$182.9394	$182.94	$182.95	$182.90
Purchase #6	$6.31	4.157%	$6.5723	$6.57	$6.55	$6.60
Purchase #7	$148.61	4.623%	$155.4802	$155.48	$155.50	$155.50
7 purchase totals =	$701.81		$762.0525	$762.05	$762.05	$762.10