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	$141.95	6.277%	$150.8602	$150.86	$150.85	$150.90
Purchase #2	$83.27	5.700%	$88.0164	$88.02	$88.00	$88.00
Purchase #3	$81.79	11.725%	$91.3799	$91.38	$91.40	$91.40
Purchase #4	$141.92	13.257%	$160.7343	$160.73	$160.75	$160.70
Purchase #5	$34.88	11.196%	$38.7852	$38.79	$38.80	$38.80
Purchase #6	$44.44	4.654%	$46.5082	$46.51	$46.50	$46.50
Purchase #7	$130.57	6.818%	$139.4723	$139.47	$139.45	$139.50
7 purchase totals =	$658.82		$715.7565	$715.76	$715.75	$715.80