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	$67.29	8.595%	$73.0736	$73.07	$73.05	$73.10
Purchase #2	$79.69	13.844%	$90.7223	$90.72	$90.70	$90.70
Purchase #3	$33.57	9.781%	$36.8535	$36.85	$36.85	$36.90
Purchase #4	$118.90	10.249%	$131.0861	$131.09	$131.10	$131.10
Purchase #5	$208.70	11.848%	$233.4268	$233.43	$233.45	$233.40
Purchase #6	$132.60	8.503%	$143.875	$143.88	$143.90	$143.90
Purchase #7	$27.58	13.802%	$31.3866	$31.39	$31.40	$31.40
7 purchase totals =	$668.33		$740.4239	$740.43	$740.45	$740.50