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	$83.92	10.753%	$92.9439	$92.94	$92.95	$92.90
Purchase #2	$53.74	11.434%	$59.8846	$59.88	$59.90	$59.90
Purchase #3	$221.94	9.138%	$242.2209	$242.22	$242.20	$242.20
Purchase #4	$6.61	11.767%	$7.3878	$7.39	$7.40	$7.40
Purchase #5	$116.63	13.347%	$132.1966	$132.20	$132.20	$132.20
Purchase #6	$141.66	3.420%	$146.5048	$146.50	$146.50	$146.50
Purchase #7	$42.75	4.294%	$44.5857	$44.59	$44.60	$44.60
7 purchase totals =	$667.25		$725.7243	$725.72	$725.75	$725.70