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	$235.97	9.682%	$258.8166	$258.82	$258.80	$258.80
Purchase #2	$160.78	11.652%	$179.5141	$179.51	$179.50	$179.50
Purchase #3	$47.60	11.618%	$53.1302	$53.13	$53.15	$53.10
Purchase #4	$140.76	9.820%	$154.5826	$154.58	$154.60	$154.60
Purchase #5	$93.88	6.375%	$99.8649	$99.86	$99.85	$99.90
Purchase #6	$97.55	3.799%	$101.2559	$101.26	$101.25	$101.30
Purchase #7	$152.30	8.337%	$164.9973	$165.00	$165.00	$165.00
7 purchase totals =	$928.84		$1,012.1616	$1,012.16	$1,012.15	$1,012.20