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	$89.68	12.435%	$100.8317	$100.83	$100.85	$100.80
Purchase #2	$63.35	9.672%	$69.4772	$69.48	$69.50	$69.50
Purchase #3	$110.26	8.350%	$119.4667	$119.47	$119.45	$119.50
Purchase #4	$211.77	6.796%	$226.1619	$226.16	$226.15	$226.20
Purchase #5	$165.31	4.700%	$173.0796	$173.08	$173.10	$173.10
Purchase #6	$98.31	9.317%	$107.4695	$107.47	$107.45	$107.50
Purchase #7	$235.57	12.679%	$265.4379	$265.44	$265.45	$265.40
7 purchase totals =	$974.25		$1,061.9245	$1,061.93	$1,061.95	$1,062.00