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	$33.94	11.104%	$37.7087	$37.71	$37.70	$37.70
Purchase #2	$61.73	6.194%	$65.5536	$65.55	$65.55	$65.60
Purchase #3	$48.96	11.360%	$54.5219	$54.52	$54.50	$54.50
Purchase #4	$208.50	7.368%	$223.8623	$223.86	$223.85	$223.90
Purchase #5	$18.48	12.152%	$20.7257	$20.73	$20.75	$20.70
Purchase #6	$235.49	8.325%	$255.0945	$255.09	$255.10	$255.10
Purchase #7	$44.76	11.560%	$49.9343	$49.93	$49.95	$49.90
7 purchase totals =	$651.86		$707.4010	$707.39	$707.40	$707.40