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	$60.69	13.583%	$68.9335	$68.93	$68.95	$68.90
Purchase #2	$85.57	5.754%	$90.4937	$90.49	$90.50	$90.50
Purchase #3	$184.69	11.602%	$206.1177	$206.12	$206.10	$206.10
Purchase #4	$63.61	6.118%	$67.5017	$67.50	$67.50	$67.50
Purchase #5	$106.79	4.793%	$111.9084	$111.91	$111.90	$111.90
Purchase #6	$22.99	6.147%	$24.4032	$24.40	$24.40	$24.40
Purchase #7	$179.71	5.184%	$189.0262	$189.03	$189.05	$189.00
7 purchase totals =	$704.05		$758.3844	$758.38	$758.40	$758.30