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	$123.48	6.499%	$131.505	$131.51	$131.50	$131.50
Purchase #2	$7.71	12.537%	$8.6766	$8.68	$8.70	$8.70
Purchase #3	$125.34	4.645%	$131.162	$131.16	$131.15	$131.20
Purchase #4	$184.51	11.253%	$205.2729	$205.27	$205.25	$205.30
Purchase #5	$54.88	10.358%	$60.5645	$60.56	$60.55	$60.60
Purchase #6	$83.56	13.590%	$94.9158	$94.92	$94.90	$94.90
Purchase #7	$189.90	13.146%	$214.8643	$214.86	$214.85	$214.90
7 purchase totals =	$769.38		$846.9611	$846.96	$846.90	$847.10