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	$95.66	7.181%	$102.5293	$102.53	$102.55	$102.50
Purchase #2	$213.64	4.541%	$223.3414	$223.34	$223.35	$223.30
Purchase #3	$75.57	3.696%	$78.3631	$78.36	$78.35	$78.40
Purchase #4	$58.46	7.579%	$62.8907	$62.89	$62.90	$62.90
Purchase #5	$97.98	7.388%	$105.2188	$105.22	$105.20	$105.20
Purchase #6	$129.64	11.218%	$144.183	$144.18	$144.20	$144.20
Purchase #7	$132.71	12.501%	$149.3001	$149.30	$149.30	$149.30
7 purchase totals =	$803.66		$865.8264	$865.82	$865.85	$865.80