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	$146.64	12.282%	$164.6503	$164.65	$164.65	$164.70
Purchase #2	$110.47	6.679%	$117.8483	$117.85	$117.85	$117.80
Purchase #3	$235.35	4.246%	$245.343	$245.34	$245.35	$245.30
Purchase #4	$246.80	12.543%	$277.7561	$277.76	$277.75	$277.80
Purchase #5	$73.70	6.568%	$78.5406	$78.54	$78.55	$78.50
Purchase #6	$158.49	3.790%	$164.4968	$164.50	$164.50	$164.50
Purchase #7	$65.59	8.826%	$71.379	$71.38	$71.40	$71.40
7 purchase totals =	$1,037.04		$1,120.0141	$1,120.02	$1,120.05	$1,120.00