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	$157.27	7.116%	$168.4613	$168.46	$168.45	$168.50
Purchase #2	$250.31	5.738%	$264.6728	$264.67	$264.65	$264.70
Purchase #3	$236.70	11.514%	$263.9536	$263.95	$263.95	$264.00
Purchase #4	$169.81	3.641%	$175.9928	$175.99	$176.00	$176.00
Purchase #5	$34.37	8.321%	$37.2299	$37.23	$37.25	$37.20
Purchase #6	$116.80	5.327%	$123.0219	$123.02	$123.00	$123.00
Purchase #7	$25.82	5.134%	$27.1456	$27.15	$27.15	$27.10
7 purchase totals =	$991.08		$1,060.4779	$1,060.47	$1,060.45	$1,060.50