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	$133.33	12.423%	$149.8936	$149.89	$149.90	$149.90
Purchase #2	$82.78	3.389%	$85.5854	$85.59	$85.60	$85.60
Purchase #3	$6.65	12.388%	$7.4738	$7.47	$7.45	$7.50
Purchase #4	$150.90	11.518%	$168.2807	$168.28	$168.30	$168.30
Purchase #5	$56.69	5.452%	$59.7807	$59.78	$59.80	$59.80
Purchase #6	$206.99	6.815%	$221.0964	$221.10	$221.10	$221.10
Purchase #7	$241.63	9.320%	$264.1499	$264.15	$264.15	$264.10
7 purchase totals =	$878.97		$956.2605	$956.26	$956.30	$956.30