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	$62.32	11.211%	$69.3067	$69.31	$69.30	$69.30
Purchase #2	$221.65	10.304%	$244.4888	$244.49	$244.50	$244.50
Purchase #3	$140.45	13.834%	$159.8799	$159.88	$159.90	$159.90
Purchase #4	$84.25	7.238%	$90.348	$90.35	$90.35	$90.30
Purchase #5	$179.48	11.829%	$200.7107	$200.71	$200.70	$200.70
Purchase #6	$84.33	5.250%	$88.7573	$88.76	$88.75	$88.80
Purchase #7	$98.66	13.246%	$111.7285	$111.73	$111.75	$111.70
7 purchase totals =	$871.14		$965.2199	$965.23	$965.25	$965.20