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	$204.72	7.601%	$220.2808	$220.28	$220.30	$220.30
Purchase #2	$239.53	10.831%	$265.4735	$265.47	$265.45	$265.50
Purchase #3	$168.94	10.389%	$186.4912	$186.49	$186.50	$186.50
Purchase #4	$175.41	12.148%	$196.7188	$196.72	$196.70	$196.70
Purchase #5	$162.86	7.478%	$175.0387	$175.04	$175.05	$175.00
Purchase #6	$126.67	10.133%	$139.5055	$139.51	$139.50	$139.50
Purchase #7	$97.49	6.517%	$103.8434	$103.84	$103.85	$103.80
7 purchase totals =	$1,175.62		$1,287.3519	$1,287.35	$1,287.35	$1,287.30