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	$119.25	12.722%	$134.421	$134.42	$134.40	$134.40
Purchase #2	$213.76	13.539%	$242.701	$242.70	$242.70	$242.70
Purchase #3	$17.86	3.468%	$18.4794	$18.48	$18.50	$18.50
Purchase #4	$38.94	9.142%	$42.4999	$42.50	$42.50	$42.50
Purchase #5	$165.56	9.254%	$180.8809	$180.88	$180.90	$180.90
Purchase #6	$32.75	13.136%	$37.052	$37.05	$37.05	$37.10
Purchase #7	$150.31	12.307%	$168.8087	$168.81	$168.80	$168.80
7 purchase totals =	$738.43		$824.8429	$824.84	$824.85	$824.90