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	$31.57	4.804%	$33.0866	$33.09	$33.10	$33.10
Purchase #2	$48.41	9.361%	$52.9417	$52.94	$52.95	$52.90
Purchase #3	$133.40	4.444%	$139.3283	$139.33	$139.35	$139.30
Purchase #4	$31.30	4.677%	$32.7639	$32.76	$32.75	$32.80
Purchase #5	$86.60	8.595%	$94.0433	$94.04	$94.05	$94.00
Purchase #6	$97.57	4.420%	$101.8826	$101.88	$101.90	$101.90
Purchase #7	$216.71	12.817%	$244.4857	$244.49	$244.50	$244.50
7 purchase totals =	$645.56		$698.5321	$698.53	$698.60	$698.50