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	$232.96	5.553%	$245.8963	$245.90	$245.90	$245.90
Purchase #2	$17.93	13.714%	$20.3889	$20.39	$20.40	$20.40
Purchase #3	$228.51	12.752%	$257.6496	$257.65	$257.65	$257.60
Purchase #4	$169.61	6.407%	$180.4769	$180.48	$180.50	$180.50
Purchase #5	$141.92	12.111%	$159.1079	$159.11	$159.10	$159.10
Purchase #6	$193.67	13.413%	$219.647	$219.65	$219.65	$219.60
Purchase #7	$101.90	10.759%	$112.8634	$112.86	$112.85	$112.90
7 purchase totals =	$1,086.50		$1,196.0300	$1,196.04	$1,196.05	$1,196.00