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	$134.67	5.157%	$141.6149	$141.61	$141.60	$141.60
Purchase #2	$173.69	11.631%	$193.8919	$193.89	$193.90	$193.90
Purchase #3	$37.91	6.286%	$40.293	$40.29	$40.30	$40.30
Purchase #4	$18.72	5.556%	$19.7601	$19.76	$19.75	$19.80
Purchase #5	$80.93	5.616%	$85.475	$85.48	$85.50	$85.50
Purchase #6	$39.27	11.518%	$43.7931	$43.79	$43.80	$43.80
Purchase #7	$165.87	11.405%	$184.7875	$184.79	$184.80	$184.80
7 purchase totals =	$651.06		$709.6155	$709.61	$709.65	$709.70