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	$82.79	9.735%	$90.8496	$90.85	$90.85	$90.80
Purchase #2	$189.81	13.377%	$215.2009	$215.20	$215.20	$215.20
Purchase #3	$151.94	9.851%	$166.9076	$166.91	$166.90	$166.90
Purchase #4	$169.93	11.872%	$190.1041	$190.10	$190.10	$190.10
Purchase #5	$183.25	5.800%	$193.8785	$193.88	$193.90	$193.90
Purchase #6	$83.28	11.529%	$92.8814	$92.88	$92.90	$92.90
Purchase #7	$137.49	4.765%	$144.0414	$144.04	$144.05	$144.00
7 purchase totals =	$998.49		$1,093.8635	$1,093.86	$1,093.90	$1,093.80