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	$230.41	5.732%	$243.6171	$243.62	$243.60	$243.60
Purchase #2	$204.76	8.410%	$221.9803	$221.98	$222.00	$222.00
Purchase #3	$159.40	12.834%	$179.8574	$179.86	$179.85	$179.90
Purchase #4	$19.47	3.484%	$20.1483	$20.15	$20.15	$20.10
Purchase #5	$230.72	6.720%	$246.2244	$246.22	$246.20	$246.20
Purchase #6	$125.60	9.374%	$137.3737	$137.37	$137.35	$137.40
Purchase #7	$196.28	4.840%	$205.78	$205.78	$205.80	$205.80
7 purchase totals =	$1,166.64		$1,254.9812	$1,254.98	$1,254.95	$1,255.00