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	$234.62	11.434%	$261.4465	$261.45	$261.45	$261.40
Purchase #2	$18.67	12.696%	$21.0403	$21.04	$21.05	$21.00
Purchase #3	$89.63	7.324%	$96.1945	$96.19	$96.20	$96.20
Purchase #4	$10.52	8.590%	$11.4237	$11.42	$11.40	$11.40
Purchase #5	$164.79	4.534%	$172.2616	$172.26	$172.25	$172.30
Purchase #6	$90.61	9.537%	$99.2515	$99.25	$99.25	$99.30
Purchase #7	$198.48	9.473%	$217.282	$217.28	$217.30	$217.30
7 purchase totals =	$807.32		$878.9001	$878.89	$878.90	$878.90