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	$182.62	12.781%	$205.9607	$205.96	$205.95	$206.00
Purchase #2	$8.90	12.531%	$10.0153	$10.02	$10.00	$10.00
Purchase #3	$165.58	3.609%	$171.5558	$171.56	$171.55	$171.60
Purchase #4	$82.76	11.682%	$92.428	$92.43	$92.45	$92.40
Purchase #5	$194.91	13.826%	$221.8583	$221.86	$221.85	$221.90
Purchase #6	$34.79	6.549%	$37.0684	$37.07	$37.05	$37.10
Purchase #7	$187.27	13.439%	$212.4372	$212.44	$212.45	$212.40
7 purchase totals =	$856.83		$951.3237	$951.34	$951.30	$951.40