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	$75.93	12.371%	$85.3233	$85.32	$85.30	$85.30
Purchase #2	$48.56	12.132%	$54.4513	$54.45	$54.45	$54.50
Purchase #3	$19.80	5.105%	$20.8108	$20.81	$20.80	$20.80
Purchase #4	$7.29	6.423%	$7.7582	$7.76	$7.75	$7.80
Purchase #5	$13.69	11.336%	$15.2419	$15.24	$15.25	$15.20
Purchase #6	$6.77	13.642%	$7.6936	$7.69	$7.70	$7.70
Purchase #7	$238.81	11.366%	$265.9531	$265.95	$265.95	$266.00
7 purchase totals =	$410.85		$457.2322	$457.22	$457.20	$457.30