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	$155.33	11.280%	$172.8512	$172.85	$172.85	$172.90
Purchase #2	$78.31	13.428%	$88.8255	$88.83	$88.85	$88.80
Purchase #3	$40.91	7.461%	$43.9623	$43.96	$43.95	$44.00
Purchase #4	$135.47	12.684%	$152.653	$152.65	$152.65	$152.70
Purchase #5	$212.42	4.765%	$222.5418	$222.54	$222.55	$222.50
Purchase #6	$218.61	12.640%	$246.2423	$246.24	$246.25	$246.20
Purchase #7	$27.53	9.511%	$30.1484	$30.15	$30.15	$30.10
7 purchase totals =	$868.58		$957.2245	$957.22	$957.25	$957.20