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	$89.43	6.809%	$95.5193	$95.52	$95.50	$95.50
Purchase #2	$205.44	10.301%	$226.6024	$226.60	$226.60	$226.60
Purchase #3	$182.27	9.444%	$199.4836	$199.48	$199.50	$199.50
Purchase #4	$50.92	5.874%	$53.911	$53.91	$53.90	$53.90
Purchase #5	$218.90	13.342%	$248.1056	$248.11	$248.10	$248.10
Purchase #6	$132.79	4.235%	$138.4137	$138.41	$138.40	$138.40
Purchase #7	$176.79	7.818%	$190.6114	$190.61	$190.60	$190.60
7 purchase totals =	$1,056.54		$1,152.6470	$1,152.64	$1,152.60	$1,152.60