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	$133.25	5.857%	$141.0545	$141.05	$141.05	$141.10
Purchase #2	$113.48	12.232%	$127.3609	$127.36	$127.35	$127.40
Purchase #3	$40.44	3.705%	$41.9383	$41.94	$41.95	$41.90
Purchase #4	$130.37	7.114%	$139.6445	$139.64	$139.65	$139.60
Purchase #5	$34.27	9.623%	$37.5678	$37.57	$37.55	$37.60
Purchase #6	$40.45	11.216%	$44.9869	$44.99	$45.00	$45.00
Purchase #7	$134.56	6.404%	$143.1772	$143.18	$143.20	$143.20
7 purchase totals =	$626.82		$675.7301	$675.73	$675.75	$675.80