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	$146.29	4.400%	$152.7268	$152.73	$152.75	$152.70
Purchase #2	$242.48	9.189%	$264.7615	$264.76	$264.75	$264.80
Purchase #3	$156.70	6.194%	$166.406	$166.41	$166.40	$166.40
Purchase #4	$235.47	8.797%	$256.1843	$256.18	$256.20	$256.20
Purchase #5	$33.36	13.498%	$37.8629	$37.86	$37.85	$37.90
Purchase #6	$41.71	4.637%	$43.6441	$43.64	$43.65	$43.60
Purchase #7	$33.41	6.148%	$35.464	$35.46	$35.45	$35.50
7 purchase totals =	$889.42		$957.0496	$957.04	$957.05	$957.10