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	$89.44	3.837%	$92.8718	$92.87	$92.85	$92.90
Purchase #2	$184.83	7.388%	$198.4852	$198.49	$198.50	$198.50
Purchase #3	$209.86	11.313%	$233.6015	$233.60	$233.60	$233.60
Purchase #4	$44.83	8.831%	$48.7889	$48.79	$48.80	$48.80
Purchase #5	$239.31	7.740%	$257.8326	$257.83	$257.85	$257.80
Purchase #6	$137.50	5.313%	$144.8054	$144.81	$144.80	$144.80
Purchase #7	$238.70	11.257%	$265.5705	$265.57	$265.55	$265.60
7 purchase totals =	$1,144.47		$1,241.9559	$1,241.96	$1,241.95	$1,242.00