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	$170.59	13.485%	$193.5941	$193.59	$193.60	$193.60
Purchase #2	$59.36	9.564%	$65.0372	$65.04	$65.05	$65.00
Purchase #3	$56.74	4.677%	$59.3937	$59.39	$59.40	$59.40
Purchase #4	$176.89	4.429%	$184.7245	$184.72	$184.70	$184.70
Purchase #5	$18.29	10.843%	$20.2732	$20.27	$20.25	$20.30
Purchase #6	$219.91	8.673%	$238.9828	$238.98	$239.00	$239.00
Purchase #7	$38.94	4.633%	$40.7441	$40.74	$40.75	$40.70
7 purchase totals =	$740.72		$802.7496	$802.73	$802.75	$802.70