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	$248.62	9.137%	$271.3364	$271.34	$271.35	$271.30
Purchase #2	$26.30	8.845%	$28.6262	$28.63	$28.65	$28.60
Purchase #3	$33.43	12.137%	$37.4874	$37.49	$37.50	$37.50
Purchase #4	$64.82	13.331%	$73.4612	$73.46	$73.45	$73.50
Purchase #5	$217.76	5.566%	$229.8805	$229.88	$229.90	$229.90
Purchase #6	$45.48	6.318%	$48.3534	$48.35	$48.35	$48.40
Purchase #7	$35.36	6.141%	$37.5315	$37.53	$37.55	$37.50
7 purchase totals =	$671.77		$726.6766	$726.68	$726.75	$726.70