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	$189.90	13.462%	$215.4643	$215.46	$215.45	$215.50
Purchase #2	$53.59	3.546%	$55.4903	$55.49	$55.50	$55.50
Purchase #3	$145.67	12.253%	$163.5189	$163.52	$163.50	$163.50
Purchase #4	$18.76	11.139%	$20.8497	$20.85	$20.85	$20.80
Purchase #5	$245.61	11.560%	$274.0025	$274.00	$274.00	$274.00
Purchase #6	$42.48	7.809%	$45.7973	$45.80	$45.80	$45.80
Purchase #7	$168.98	13.704%	$192.137	$192.14	$192.15	$192.10
7 purchase totals =	$864.99		$967.2600	$967.26	$967.25	$967.20