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	$133.32	4.361%	$139.1341	$139.13	$139.15	$139.10
Purchase #2	$40.70	9.240%	$44.4607	$44.46	$44.45	$44.50
Purchase #3	$137.27	13.852%	$156.2846	$156.28	$156.30	$156.30
Purchase #4	$151.93	10.224%	$167.4633	$167.46	$167.45	$167.50
Purchase #5	$67.49	6.467%	$71.8546	$71.85	$71.85	$71.90
Purchase #6	$215.71	6.111%	$228.892	$228.89	$228.90	$228.90
Purchase #7	$203.73	10.366%	$224.8487	$224.85	$224.85	$224.80
7 purchase totals =	$950.15		$1,032.9380	$1,032.92	$1,032.95	$1,033.00