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	$224.53	13.759%	$255.4231	$255.42	$255.40	$255.40
Purchase #2	$195.97	12.103%	$219.6882	$219.69	$219.70	$219.70
Purchase #3	$247.49	10.565%	$273.6373	$273.64	$273.65	$273.60
Purchase #4	$39.79	11.139%	$44.2222	$44.22	$44.20	$44.20
Purchase #5	$174.82	13.530%	$198.4731	$198.47	$198.45	$198.50
Purchase #6	$103.72	8.526%	$112.5632	$112.56	$112.55	$112.60
Purchase #7	$82.41	12.460%	$92.6783	$92.68	$92.70	$92.70
7 purchase totals =	$1,068.73		$1,196.6854	$1,196.68	$1,196.65	$1,196.70