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	$72.75	12.506%	$81.8481	$81.85	$81.85	$81.80
Purchase #2	$63.95	12.109%	$71.6937	$71.69	$71.70	$71.70
Purchase #3	$7.43	6.565%	$7.9178	$7.92	$7.90	$7.90
Purchase #4	$40.65	10.471%	$44.9065	$44.91	$44.90	$44.90
Purchase #5	$155.27	13.699%	$176.5404	$176.54	$176.55	$176.50
Purchase #6	$191.79	12.686%	$216.1205	$216.12	$216.10	$216.10
Purchase #7	$99.48	13.609%	$113.0182	$113.02	$113.00	$113.00
7 purchase totals =	$631.32		$712.0452	$712.05	$712.00	$711.90