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	$118.28	11.322%	$131.6717	$131.67	$131.65	$131.70
Purchase #2	$87.89	11.460%	$97.9622	$97.96	$97.95	$98.00
Purchase #3	$31.71	5.357%	$33.4087	$33.41	$33.40	$33.40
Purchase #4	$189.94	5.570%	$200.5197	$200.52	$200.50	$200.50
Purchase #5	$7.81	11.503%	$8.7084	$8.71	$8.70	$8.70
Purchase #6	$78.72	4.497%	$82.26	$82.26	$82.25	$82.30
Purchase #7	$238.55	13.651%	$271.1145	$271.11	$271.10	$271.10
7 purchase totals =	$752.90		$825.6452	$825.64	$825.55	$825.70