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	$171.30	12.601%	$192.8855	$192.89	$192.90	$192.90
Purchase #2	$206.97	12.819%	$233.5015	$233.50	$233.50	$233.50
Purchase #3	$58.74	12.175%	$65.8916	$65.89	$65.90	$65.90
Purchase #4	$243.69	13.869%	$277.4874	$277.49	$277.50	$277.50
Purchase #5	$14.37	3.646%	$14.8939	$14.89	$14.90	$14.90
Purchase #6	$92.54	13.689%	$105.2078	$105.21	$105.20	$105.20
Purchase #7	$182.54	3.379%	$188.708	$188.71	$188.70	$188.70
7 purchase totals =	$970.15		$1,078.5757	$1,078.58	$1,078.60	$1,078.60