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	$60.27	4.336%	$62.8833	$62.88	$62.90	$62.90
Purchase #2	$245.47	13.271%	$278.0463	$278.05	$278.05	$278.00
Purchase #3	$128.89	10.502%	$142.426	$142.43	$142.45	$142.40
Purchase #4	$62.65	6.587%	$66.7768	$66.78	$66.80	$66.80
Purchase #5	$232.27	9.870%	$255.195	$255.20	$255.20	$255.20
Purchase #6	$5.85	12.430%	$6.5772	$6.58	$6.60	$6.60
Purchase #7	$5.33	4.408%	$5.5649	$5.56	$5.55	$5.60
7 purchase totals =	$740.73		$817.4695	$817.48	$817.55	$817.50