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	$73.59	7.130%	$78.837	$78.84	$78.85	$78.80
Purchase #2	$89.59	8.522%	$97.2249	$97.22	$97.20	$97.20
Purchase #3	$127.35	11.312%	$141.7558	$141.76	$141.75	$141.80
Purchase #4	$155.79	10.421%	$172.0249	$172.02	$172.00	$172.00
Purchase #5	$43.73	10.154%	$48.1703	$48.17	$48.15	$48.20
Purchase #6	$163.61	4.796%	$171.4567	$171.46	$171.45	$171.50
Purchase #7	$222.29	5.840%	$235.2717	$235.27	$235.25	$235.30
7 purchase totals =	$875.95		$944.7413	$944.74	$944.65	$944.80