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	$152.86	8.657%	$166.0931	$166.09	$166.10	$166.10
Purchase #2	$28.73	11.830%	$32.1288	$32.13	$32.15	$32.10
Purchase #3	$149.46	8.584%	$162.2896	$162.29	$162.30	$162.30
Purchase #4	$198.31	12.706%	$223.5073	$223.51	$223.50	$223.50
Purchase #5	$45.82	10.284%	$50.5321	$50.53	$50.55	$50.50
Purchase #6	$141.31	8.610%	$153.4768	$153.48	$153.50	$153.50
Purchase #7	$127.51	11.601%	$142.3024	$142.30	$142.30	$142.30
7 purchase totals =	$844.00		$930.3301	$930.33	$930.40	$930.30