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	$234.98	4.452%	$245.4413	$245.44	$245.45	$245.40
Purchase #2	$63.60	5.273%	$66.9536	$66.95	$66.95	$67.00
Purchase #3	$38.41	11.741%	$42.9197	$42.92	$42.90	$42.90
Purchase #4	$49.93	13.493%	$56.6671	$56.67	$56.65	$56.70
Purchase #5	$204.77	8.348%	$221.8642	$221.86	$221.85	$221.90
Purchase #6	$67.48	5.633%	$71.2811	$71.28	$71.30	$71.30
Purchase #7	$245.30	6.130%	$260.3369	$260.34	$260.35	$260.30
7 purchase totals =	$904.47		$965.4639	$965.46	$965.45	$965.50