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	$170.59	6.785%	$182.1645	$182.16	$182.15	$182.20
Purchase #2	$94.90	5.863%	$100.464	$100.46	$100.45	$100.50
Purchase #3	$189.46	5.250%	$199.4067	$199.41	$199.40	$199.40
Purchase #4	$197.79	9.595%	$216.768	$216.77	$216.75	$216.80
Purchase #5	$208.54	10.393%	$230.2136	$230.21	$230.20	$230.20
Purchase #6	$205.74	6.191%	$218.4774	$218.48	$218.50	$218.50
Purchase #7	$118.65	10.816%	$131.4832	$131.48	$131.50	$131.50
7 purchase totals =	$1,185.67		$1,278.9774	$1,278.97	$1,278.95	$1,279.10