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	$13.49	10.394%	$14.8922	$14.89	$14.90	$14.90
Purchase #2	$205.27	7.103%	$219.8503	$219.85	$219.85	$219.90
Purchase #3	$105.37	7.140%	$112.8934	$112.89	$112.90	$112.90
Purchase #4	$223.97	8.290%	$242.5371	$242.54	$242.55	$242.50
Purchase #5	$53.39	7.515%	$57.4023	$57.40	$57.40	$57.40
Purchase #6	$104.69	8.810%	$113.9132	$113.91	$113.90	$113.90
Purchase #7	$108.37	10.524%	$119.7749	$119.77	$119.75	$119.80
7 purchase totals =	$814.55		$881.2634	$881.25	$881.25	$881.30