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	$140.72	7.226%	$150.8884	$150.89	$150.90	$150.90
Purchase #2	$19.70	3.401%	$20.37	$20.37	$20.35	$20.40
Purchase #3	$44.69	11.406%	$49.7873	$49.79	$49.80	$49.80
Purchase #4	$117.47	10.601%	$129.923	$129.92	$129.90	$129.90
Purchase #5	$85.95	4.326%	$89.6682	$89.67	$89.65	$89.70
Purchase #6	$64.94	10.137%	$71.523	$71.52	$71.50	$71.50
Purchase #7	$131.77	7.835%	$142.0942	$142.09	$142.10	$142.10
7 purchase totals =	$605.24		$654.2541	$654.25	$654.20	$654.30