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	$82.28	9.263%	$89.9016	$89.90	$89.90	$89.90
Purchase #2	$117.93	11.674%	$131.6971	$131.70	$131.70	$131.70
Purchase #3	$87.96	4.636%	$92.0378	$92.04	$92.05	$92.00
Purchase #4	$24.57	4.112%	$25.5803	$25.58	$25.60	$25.60
Purchase #5	$101.47	12.142%	$113.7905	$113.79	$113.80	$113.80
Purchase #6	$65.67	8.744%	$71.4122	$71.41	$71.40	$71.40
Purchase #7	$156.73	9.170%	$171.1021	$171.10	$171.10	$171.10
7 purchase totals =	$636.61		$695.5216	$695.52	$695.55	$695.50