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	$98.73	9.221%	$107.8339	$107.83	$107.85	$107.80
Purchase #2	$211.47	6.178%	$224.5346	$224.53	$224.55	$224.50
Purchase #3	$121.43	4.506%	$126.9016	$126.90	$126.90	$126.90
Purchase #4	$98.83	10.840%	$109.5432	$109.54	$109.55	$109.50
Purchase #5	$113.54	3.482%	$117.4935	$117.49	$117.50	$117.50
Purchase #6	$140.28	11.303%	$156.1358	$156.14	$156.15	$156.10
Purchase #7	$174.85	10.331%	$192.9138	$192.91	$192.90	$192.90
7 purchase totals =	$959.13		$1,035.3564	$1,035.34	$1,035.40	$1,035.20