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	$75.71	13.452%	$85.8945	$85.89	$85.90	$85.90
Purchase #2	$93.79	9.265%	$102.4796	$102.48	$102.50	$102.50
Purchase #3	$166.87	11.401%	$185.8948	$185.89	$185.90	$185.90
Purchase #4	$9.85	9.440%	$10.7798	$10.78	$10.80	$10.80
Purchase #5	$200.73	9.743%	$220.2871	$220.29	$220.30	$220.30
Purchase #6	$58.57	6.637%	$62.4573	$62.46	$62.45	$62.50
Purchase #7	$141.81	6.678%	$151.2801	$151.28	$151.30	$151.30
7 purchase totals =	$747.33		$819.0732	$819.07	$819.15	$819.20