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	$136.43	10.860%	$151.2463	$151.25	$151.25	$151.20
Purchase #2	$225.51	4.577%	$235.8316	$235.83	$235.85	$235.80
Purchase #3	$68.68	12.503%	$77.2671	$77.27	$77.25	$77.30
Purchase #4	$10.69	6.142%	$11.3466	$11.35	$11.35	$11.30
Purchase #5	$240.54	4.297%	$250.876	$250.88	$250.90	$250.90
Purchase #6	$64.64	11.315%	$71.954	$71.95	$71.95	$72.00
Purchase #7	$136.43	6.453%	$145.2338	$145.23	$145.25	$145.20
7 purchase totals =	$882.92		$943.7554	$943.76	$943.80	$943.70