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	$134.99	11.221%	$150.1372	$150.14	$150.15	$150.10
Purchase #2	$33.30	11.475%	$37.1212	$37.12	$37.10	$37.10
Purchase #3	$33.28	8.375%	$36.0672	$36.07	$36.05	$36.10
Purchase #4	$185.60	3.500%	$192.096	$192.10	$192.10	$192.10
Purchase #5	$24.82	13.444%	$28.1568	$28.16	$28.15	$28.20
Purchase #6	$75.73	6.329%	$80.523	$80.52	$80.50	$80.50
Purchase #7	$27.77	13.539%	$31.5298	$31.53	$31.55	$31.50
7 purchase totals =	$515.49		$555.6312	$555.64	$555.60	$555.60