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	$219.60	3.111%	$226.4318	$226.43	$226.45	$226.40
Purchase #2	$185.74	5.681%	$196.2919	$196.29	$196.30	$196.30
Purchase #3	$6.89	12.507%	$7.7517	$7.75	$7.75	$7.80
Purchase #4	$212.89	6.767%	$227.2963	$227.30	$227.30	$227.30
Purchase #5	$75.45	3.140%	$77.8191	$77.82	$77.80	$77.80
Purchase #6	$36.27	4.125%	$37.7661	$37.77	$37.75	$37.80
Purchase #7	$34.43	6.282%	$36.5929	$36.59	$36.60	$36.60
7 purchase totals =	$771.27		$809.9498	$809.95	$809.95	$810.00