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	$146.73	6.380%	$156.0914	$156.09	$156.10	$156.10
Purchase #2	$37.37	8.255%	$40.4549	$40.45	$40.45	$40.50
Purchase #3	$182.33	9.864%	$200.315	$200.32	$200.30	$200.30
Purchase #4	$24.98	12.857%	$28.1917	$28.19	$28.20	$28.20
Purchase #5	$154.89	11.135%	$172.137	$172.14	$172.15	$172.10
Purchase #6	$113.61	3.229%	$117.2785	$117.28	$117.30	$117.30
Purchase #7	$12.96	7.593%	$13.9441	$13.94	$13.95	$13.90
7 purchase totals =	$672.87		$728.4126	$728.41	$728.45	$728.40