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	$67.76	5.483%	$71.4753	$71.48	$71.50	$71.50
Purchase #2	$217.95	7.421%	$234.1241	$234.12	$234.10	$234.10
Purchase #3	$151.38	12.832%	$170.8051	$170.81	$170.80	$170.80
Purchase #4	$32.48	10.300%	$35.8254	$35.83	$35.85	$35.80
Purchase #5	$131.51	5.783%	$139.1152	$139.12	$139.10	$139.10
Purchase #6	$189.86	5.382%	$200.0783	$200.08	$200.10	$200.10
Purchase #7	$97.53	3.647%	$101.0869	$101.09	$101.10	$101.10
7 purchase totals =	$888.47		$952.5103	$952.53	$952.55	$952.50