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	$125.77	8.467%	$136.4189	$136.42	$136.40	$136.40
Purchase #2	$86.43	13.567%	$98.156	$98.16	$98.15	$98.20
Purchase #3	$43.51	7.484%	$46.7663	$46.77	$46.75	$46.80
Purchase #4	$175.71	11.548%	$196.001	$196.00	$196.00	$196.00
Purchase #5	$153.75	9.774%	$168.7775	$168.78	$168.80	$168.80
Purchase #6	$141.28	3.279%	$145.9126	$145.91	$145.90	$145.90
Purchase #7	$221.88	8.667%	$241.1103	$241.11	$241.10	$241.10
7 purchase totals =	$948.33		$1,033.1426	$1,033.15	$1,033.10	$1,033.20