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	$202.82	9.754%	$222.6031	$222.60	$222.60	$222.60
Purchase #2	$52.45	11.650%	$58.5604	$58.56	$58.55	$58.60
Purchase #3	$67.84	13.684%	$77.1232	$77.12	$77.10	$77.10
Purchase #4	$133.51	6.432%	$142.0974	$142.10	$142.10	$142.10
Purchase #5	$16.95	5.530%	$17.8873	$17.89	$17.90	$17.90
Purchase #6	$156.82	3.230%	$161.8853	$161.89	$161.90	$161.90
Purchase #7	$148.61	11.529%	$165.7432	$165.74	$165.75	$165.70
7 purchase totals =	$779.00		$845.8999	$845.90	$845.90	$845.90