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	$14.69	7.454%	$15.785	$15.79	$15.80	$15.80
Purchase #2	$37.40	5.722%	$39.54	$39.54	$39.55	$39.50
Purchase #3	$36.69	11.328%	$40.8462	$40.85	$40.85	$40.80
Purchase #4	$31.54	4.695%	$33.0208	$33.02	$33.00	$33.00
Purchase #5	$162.43	4.522%	$169.7751	$169.78	$169.80	$169.80
Purchase #6	$74.91	10.612%	$82.8594	$82.86	$82.85	$82.90
Purchase #7	$13.76	6.547%	$14.6609	$14.66	$14.65	$14.70
7 purchase totals =	$371.42		$396.4874	$396.50	$396.50	$396.50