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	$35.34	7.760%	$38.0824	$38.08	$38.10	$38.10
Purchase #2	$11.60	11.260%	$12.9062	$12.91	$12.90	$12.90
Purchase #3	$74.86	9.638%	$82.075	$82.08	$82.10	$82.10
Purchase #4	$112.92	6.208%	$119.9301	$119.93	$119.95	$119.90
Purchase #5	$66.42	7.818%	$71.6127	$71.61	$71.60	$71.60
Purchase #6	$144.84	4.223%	$150.9566	$150.96	$150.95	$151.00
Purchase #7	$167.43	3.816%	$173.8191	$173.82	$173.80	$173.80
7 purchase totals =	$613.41		$649.3821	$649.39	$649.40	$649.40