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	$143.69	5.184%	$151.1389	$151.14	$151.15	$151.10
Purchase #2	$145.30	6.246%	$154.3754	$154.38	$154.40	$154.40
Purchase #3	$40.51	7.266%	$43.4535	$43.45	$43.45	$43.50
Purchase #4	$134.30	7.132%	$143.8783	$143.88	$143.90	$143.90
Purchase #5	$70.37	9.838%	$77.293	$77.29	$77.30	$77.30
Purchase #6	$152.67	8.677%	$165.9172	$165.92	$165.90	$165.90
Purchase #7	$93.64	6.401%	$99.6339	$99.63	$99.65	$99.60
7 purchase totals =	$780.48		$835.6902	$835.69	$835.75	$835.70