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	$95.51	6.722%	$101.9302	$101.93	$101.95	$101.90
Purchase #2	$55.73	10.380%	$61.5148	$61.51	$61.50	$61.50
Purchase #3	$164.91	8.184%	$178.4062	$178.41	$178.40	$178.40
Purchase #4	$83.50	5.442%	$88.0441	$88.04	$88.05	$88.00
Purchase #5	$90.85	4.691%	$95.1118	$95.11	$95.10	$95.10
Purchase #6	$124.29	12.502%	$139.8287	$139.83	$139.85	$139.80
Purchase #7	$45.74	5.163%	$48.1016	$48.10	$48.10	$48.10
7 purchase totals =	$660.53		$712.9374	$712.93	$712.95	$712.80