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	$179.54	5.853%	$190.0485	$190.05	$190.05	$190.00
Purchase #2	$12.85	4.267%	$13.3983	$13.40	$13.40	$13.40
Purchase #3	$222.56	10.346%	$245.5861	$245.59	$245.60	$245.60
Purchase #4	$97.89	11.603%	$109.2482	$109.25	$109.25	$109.20
Purchase #5	$98.29	8.393%	$106.5395	$106.54	$106.55	$106.50
Purchase #6	$181.35	6.572%	$193.2683	$193.27	$193.25	$193.30
Purchase #7	$10.48	3.864%	$10.8849	$10.88	$10.90	$10.90
7 purchase totals =	$802.96		$868.9738	$868.98	$869.00	$868.90