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	$172.76	12.825%	$194.9165	$194.92	$194.90	$194.90
Purchase #2	$117.55	12.201%	$131.8923	$131.89	$131.90	$131.90
Purchase #3	$80.75	12.106%	$90.5256	$90.53	$90.55	$90.50
Purchase #4	$102.82	3.855%	$106.7837	$106.78	$106.80	$106.80
Purchase #5	$23.50	10.842%	$26.0479	$26.05	$26.05	$26.00
Purchase #6	$140.46	10.267%	$154.881	$154.88	$154.90	$154.90
Purchase #7	$30.81	10.141%	$33.9344	$33.93	$33.95	$33.90
7 purchase totals =	$668.65		$738.9814	$738.98	$739.05	$738.90