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	$136.39	7.829%	$147.068	$147.07	$147.05	$147.10
Purchase #2	$212.53	13.636%	$241.5106	$241.51	$241.50	$241.50
Purchase #3	$233.71	6.193%	$248.1837	$248.18	$248.20	$248.20
Purchase #4	$247.35	3.467%	$255.9256	$255.93	$255.95	$255.90
Purchase #5	$249.54	10.405%	$275.5046	$275.50	$275.50	$275.50
Purchase #6	$38.80	8.197%	$41.9804	$41.98	$42.00	$42.00
Purchase #7	$210.90	3.773%	$218.8573	$218.86	$218.85	$218.90
7 purchase totals =	$1,329.22		$1,429.0302	$1,429.03	$1,429.05	$1,429.10