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	$124.85	5.480%	$131.6918	$131.69	$131.70	$131.70
Purchase #2	$221.52	10.219%	$244.1571	$244.16	$244.15	$244.20
Purchase #3	$25.87	10.772%	$28.6567	$28.66	$28.65	$28.70
Purchase #4	$34.52	5.266%	$36.3378	$36.34	$36.35	$36.30
Purchase #5	$233.59	5.863%	$247.2854	$247.29	$247.30	$247.30
Purchase #6	$220.46	11.461%	$245.7269	$245.73	$245.75	$245.70
Purchase #7	$219.34	6.498%	$233.5927	$233.59	$233.60	$233.60
7 purchase totals =	$1,080.15		$1,167.4484	$1,167.46	$1,167.50	$1,167.50