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	$88.60	8.480%	$96.1133	$96.11	$96.10	$96.10
Purchase #2	$78.50	10.186%	$86.496	$86.50	$86.50	$86.50
Purchase #3	$82.31	9.516%	$90.1426	$90.14	$90.15	$90.10
Purchase #4	$68.76	4.422%	$71.8006	$71.80	$71.80	$71.80
Purchase #5	$118.48	13.677%	$134.6845	$134.68	$134.70	$134.70
Purchase #6	$127.71	7.742%	$137.5973	$137.60	$137.60	$137.60
Purchase #7	$201.90	13.429%	$229.0132	$229.01	$229.00	$229.00
7 purchase totals =	$766.26		$845.8475	$845.84	$845.85	$845.80