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	$85.62	13.124%	$96.8568	$96.86	$96.85	$96.90
Purchase #2	$122.94	6.195%	$130.5561	$130.56	$130.55	$130.60
Purchase #3	$126.71	4.456%	$132.3562	$132.36	$132.35	$132.40
Purchase #4	$179.37	11.789%	$200.5159	$200.52	$200.50	$200.50
Purchase #5	$24.77	12.286%	$27.8132	$27.81	$27.80	$27.80
Purchase #6	$155.40	10.160%	$171.1886	$171.19	$171.20	$171.20
Purchase #7	$156.85	9.586%	$171.8856	$171.89	$171.90	$171.90
7 purchase totals =	$851.66		$931.1724	$931.19	$931.15	$931.30