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	$127.28	3.593%	$131.8532	$131.85	$131.85	$131.90
Purchase #2	$27.88	5.259%	$29.3462	$29.35	$29.35	$29.30
Purchase #3	$30.89	5.623%	$32.6269	$32.63	$32.65	$32.60
Purchase #4	$114.57	9.307%	$125.233	$125.23	$125.25	$125.20
Purchase #5	$144.77	12.530%	$162.9097	$162.91	$162.90	$162.90
Purchase #6	$207.50	7.762%	$223.6062	$223.61	$223.60	$223.60
Purchase #7	$146.54	8.552%	$159.0721	$159.07	$159.05	$159.10
7 purchase totals =	$799.43		$864.6473	$864.65	$864.65	$864.60