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	$42.25	8.190%	$45.7103	$45.71	$45.70	$45.70
Purchase #2	$215.96	5.260%	$227.3195	$227.32	$227.30	$227.30
Purchase #3	$39.90	12.599%	$44.927	$44.93	$44.95	$44.90
Purchase #4	$126.30	12.156%	$141.653	$141.65	$141.65	$141.70
Purchase #5	$218.40	3.443%	$225.9195	$225.92	$225.90	$225.90
Purchase #6	$13.59	11.726%	$15.1836	$15.18	$15.20	$15.20
Purchase #7	$183.54	4.356%	$191.535	$191.54	$191.55	$191.50
7 purchase totals =	$839.94		$892.2479	$892.25	$892.25	$892.20