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	$121.34	4.416%	$126.6984	$126.70	$126.70	$126.70
Purchase #2	$229.75	10.861%	$254.7031	$254.70	$254.70	$254.70
Purchase #3	$223.96	4.428%	$233.8769	$233.88	$233.90	$233.90
Purchase #4	$145.45	3.675%	$150.7953	$150.80	$150.80	$150.80
Purchase #5	$64.25	12.437%	$72.2408	$72.24	$72.25	$72.20
Purchase #6	$50.81	11.537%	$56.6719	$56.67	$56.65	$56.70
Purchase #7	$43.52	5.455%	$45.894	$45.89	$45.90	$45.90
7 purchase totals =	$879.08		$940.8804	$940.88	$940.90	$940.90