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	$90.74	6.759%	$96.8731	$96.87	$96.85	$96.90
Purchase #2	$122.26	6.503%	$130.2106	$130.21	$130.20	$130.20
Purchase #3	$62.40	3.871%	$64.8155	$64.82	$64.80	$64.80
Purchase #4	$131.83	4.193%	$137.3576	$137.36	$137.35	$137.40
Purchase #5	$174.57	12.699%	$196.7386	$196.74	$196.75	$196.70
Purchase #6	$165.54	4.377%	$172.7857	$172.79	$172.80	$172.80
Purchase #7	$208.25	13.560%	$236.4887	$236.49	$236.50	$236.50
7 purchase totals =	$955.59		$1,035.2698	$1,035.28	$1,035.25	$1,035.30