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	$46.63	13.246%	$52.8066	$52.81	$52.80	$52.80
Purchase #2	$48.61	8.843%	$52.9086	$52.91	$52.90	$52.90
Purchase #3	$37.84	7.384%	$40.6341	$40.63	$40.65	$40.60
Purchase #4	$35.76	6.750%	$38.1738	$38.17	$38.15	$38.20
Purchase #5	$225.47	8.443%	$244.5064	$244.51	$244.50	$244.50
Purchase #6	$73.36	6.359%	$78.025	$78.03	$78.05	$78.00
Purchase #7	$223.92	4.406%	$233.7859	$233.79	$233.80	$233.80
7 purchase totals =	$691.59		$740.8404	$740.85	$740.85	$740.80