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	$87.33	5.773%	$92.3716	$92.37	$92.35	$92.40
Purchase #2	$185.70	5.741%	$196.361	$196.36	$196.35	$196.40
Purchase #3	$145.48	7.846%	$156.8944	$156.89	$156.90	$156.90
Purchase #4	$120.95	5.712%	$127.8587	$127.86	$127.85	$127.90
Purchase #5	$217.86	4.408%	$227.4633	$227.46	$227.45	$227.50
Purchase #6	$10.59	5.319%	$11.1533	$11.15	$11.15	$11.20
Purchase #7	$99.43	7.632%	$107.0185	$107.02	$107.00	$107.00
7 purchase totals =	$867.34		$919.1208	$919.11	$919.05	$919.30