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	$201.65	3.517%	$208.742	$208.74	$208.75	$208.70
Purchase #2	$37.86	13.250%	$42.8765	$42.88	$42.90	$42.90
Purchase #3	$6.96	11.350%	$7.75	$7.75	$7.75	$7.80
Purchase #4	$219.86	10.141%	$242.156	$242.16	$242.15	$242.20
Purchase #5	$208.76	6.473%	$222.273	$222.27	$222.25	$222.30
Purchase #6	$107.75	3.467%	$111.4857	$111.49	$111.50	$111.50
Purchase #7	$105.46	10.493%	$116.5259	$116.53	$116.55	$116.50
7 purchase totals =	$888.30		$951.8091	$951.82	$951.85	$951.90