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	$93.40	11.850%	$104.4679	$104.47	$104.45	$104.50
Purchase #2	$186.37	5.484%	$196.5905	$196.59	$196.60	$196.60
Purchase #3	$48.54	13.672%	$55.1764	$55.18	$55.20	$55.20
Purchase #4	$184.66	3.749%	$191.5829	$191.58	$191.60	$191.60
Purchase #5	$140.47	8.196%	$151.9829	$151.98	$152.00	$152.00
Purchase #6	$32.56	10.609%	$36.0143	$36.01	$36.00	$36.00
Purchase #7	$222.57	10.371%	$245.6527	$245.65	$245.65	$245.70
7 purchase totals =	$908.57		$981.4676	$981.46	$981.50	$981.60