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	$147.85	11.756%	$165.2312	$165.23	$165.25	$165.20
Purchase #2	$41.50	3.628%	$43.0056	$43.01	$43.00	$43.00
Purchase #3	$83.67	6.291%	$88.9337	$88.93	$88.95	$88.90
Purchase #4	$91.85	8.828%	$99.9585	$99.96	$99.95	$100.00
Purchase #5	$133.62	7.124%	$143.1391	$143.14	$143.15	$143.10
Purchase #6	$72.42	12.290%	$81.3204	$81.32	$81.30	$81.30
Purchase #7	$167.47	3.260%	$172.9295	$172.93	$172.95	$172.90
7 purchase totals =	$738.38		$794.5180	$794.52	$794.55	$794.40