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	$147.59	8.107%	$159.5551	$159.56	$159.55	$159.60
Purchase #2	$111.47	7.233%	$119.5326	$119.53	$119.55	$119.50
Purchase #3	$22.32	12.171%	$25.0366	$25.04	$25.05	$25.00
Purchase #4	$191.92	4.465%	$200.4892	$200.49	$200.50	$200.50
Purchase #5	$33.47	12.835%	$37.7659	$37.77	$37.75	$37.80
Purchase #6	$204.37	7.483%	$219.663	$219.66	$219.65	$219.70
Purchase #7	$127.78	11.569%	$142.5629	$142.56	$142.55	$142.60
7 purchase totals =	$838.92		$904.6053	$904.61	$904.60	$904.70