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	$139.25	13.276%	$157.7368	$157.74	$157.75	$157.70
Purchase #2	$54.98	8.146%	$59.4587	$59.46	$59.45	$59.50
Purchase #3	$142.98	5.340%	$150.6151	$150.62	$150.60	$150.60
Purchase #4	$202.90	3.509%	$210.0198	$210.02	$210.00	$210.00
Purchase #5	$141.70	13.431%	$160.7317	$160.73	$160.75	$160.70
Purchase #6	$156.81	3.378%	$162.107	$162.11	$162.10	$162.10
Purchase #7	$223.77	10.323%	$246.8698	$246.87	$246.85	$246.90
7 purchase totals =	$1,062.39		$1,147.5389	$1,147.55	$1,147.50	$1,147.50