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	$78.77	9.463%	$86.224	$86.22	$86.20	$86.20
Purchase #2	$86.67	9.487%	$94.8924	$94.89	$94.90	$94.90
Purchase #3	$198.60	8.443%	$215.3678	$215.37	$215.35	$215.40
Purchase #4	$217.43	6.367%	$231.2738	$231.27	$231.25	$231.30
Purchase #5	$151.56	3.568%	$156.9677	$156.97	$156.95	$157.00
Purchase #6	$223.68	8.589%	$242.8919	$242.89	$242.90	$242.90
Purchase #7	$71.74	9.422%	$78.4993	$78.50	$78.50	$78.50
7 purchase totals =	$1,028.45		$1,106.1169	$1,106.11	$1,106.05	$1,106.20