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	$162.99	3.350%	$168.4502	$168.45	$168.45	$168.50
Purchase #2	$131.39	10.804%	$145.5854	$145.59	$145.60	$145.60
Purchase #3	$61.57	6.503%	$65.5739	$65.57	$65.55	$65.60
Purchase #4	$85.48	8.745%	$92.9552	$92.96	$92.95	$93.00
Purchase #5	$79.82	8.856%	$86.8889	$86.89	$86.90	$86.90
Purchase #6	$64.56	3.736%	$66.972	$66.97	$66.95	$67.00
Purchase #7	$153.89	13.594%	$174.8098	$174.81	$174.80	$174.80
7 purchase totals =	$739.70		$801.2354	$801.24	$801.20	$801.40