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	$90.60	5.825%	$95.8775	$95.88	$95.90	$95.90
Purchase #2	$136.76	12.168%	$153.401	$153.40	$153.40	$153.40
Purchase #3	$68.65	11.485%	$76.5345	$76.53	$76.55	$76.50
Purchase #4	$37.70	8.545%	$40.9215	$40.92	$40.90	$40.90
Purchase #5	$213.38	3.824%	$221.5397	$221.54	$221.55	$221.50
Purchase #6	$67.93	6.645%	$72.4439	$72.44	$72.45	$72.40
Purchase #7	$188.77	8.556%	$204.9212	$204.92	$204.90	$204.90
7 purchase totals =	$803.79		$865.6393	$865.63	$865.65	$865.50