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	$172.41	12.711%	$194.325	$194.33	$194.35	$194.30
Purchase #2	$233.65	10.805%	$258.8959	$258.90	$258.90	$258.90
Purchase #3	$107.72	6.686%	$114.9222	$114.92	$114.90	$114.90
Purchase #4	$44.74	13.439%	$50.7526	$50.75	$50.75	$50.80
Purchase #5	$40.30	3.493%	$41.7077	$41.71	$41.70	$41.70
Purchase #6	$242.93	13.522%	$275.779	$275.78	$275.80	$275.80
Purchase #7	$192.63	12.215%	$216.1598	$216.16	$216.15	$216.20
7 purchase totals =	$1,034.38		$1,152.5422	$1,152.55	$1,152.55	$1,152.60