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	$13.74	5.132%	$14.4451	$14.45	$14.45	$14.40
Purchase #2	$232.69	4.584%	$243.3565	$243.36	$243.35	$243.40
Purchase #3	$244.47	11.603%	$272.8359	$272.84	$272.85	$272.80
Purchase #4	$136.31	10.434%	$150.5326	$150.53	$150.55	$150.50
Purchase #5	$53.65	11.495%	$59.8171	$59.82	$59.80	$59.80
Purchase #6	$89.38	5.621%	$94.404	$94.40	$94.40	$94.40
Purchase #7	$219.38	11.587%	$244.7996	$244.80	$244.80	$244.80
7 purchase totals =	$989.62		$1,080.1908	$1,080.20	$1,080.20	$1,080.10