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	$214.65	8.228%	$232.3114	$232.31	$232.30	$232.30
Purchase #2	$103.85	7.192%	$111.3189	$111.32	$111.30	$111.30
Purchase #3	$166.57	5.413%	$175.5864	$175.59	$175.60	$175.60
Purchase #4	$229.93	13.591%	$261.1798	$261.18	$261.20	$261.20
Purchase #5	$223.38	13.415%	$253.3464	$253.35	$253.35	$253.30
Purchase #6	$223.25	11.426%	$248.7585	$248.76	$248.75	$248.80
Purchase #7	$131.90	5.810%	$139.5634	$139.56	$139.55	$139.60
7 purchase totals =	$1,293.53		$1,422.0648	$1,422.07	$1,422.05	$1,422.10