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	$68.55	3.227%	$70.7621	$70.76	$70.75	$70.80
Purchase #2	$68.38	8.668%	$74.3072	$74.31	$74.30	$74.30
Purchase #3	$162.66	3.320%	$168.0603	$168.06	$168.05	$168.10
Purchase #4	$39.90	6.530%	$42.5055	$42.51	$42.50	$42.50
Purchase #5	$167.95	13.314%	$190.3109	$190.31	$190.30	$190.30
Purchase #6	$217.57	8.546%	$236.1635	$236.16	$236.15	$236.20
Purchase #7	$214.76	12.192%	$240.9435	$240.94	$240.95	$240.90
7 purchase totals =	$939.77		$1,023.0530	$1,023.05	$1,023.00	$1,023.10