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	$7.32	3.860%	$7.6026	$7.60	$7.60	$7.60
Purchase #2	$22.95	11.423%	$25.5716	$25.57	$25.55	$25.60
Purchase #3	$102.89	5.828%	$108.8864	$108.89	$108.90	$108.90
Purchase #4	$157.49	4.667%	$164.8401	$164.84	$164.85	$164.80
Purchase #5	$108.91	4.262%	$113.5517	$113.55	$113.55	$113.60
Purchase #6	$78.85	5.715%	$83.3563	$83.36	$83.35	$83.40
Purchase #7	$11.45	11.155%	$12.7272	$12.73	$12.75	$12.70
7 purchase totals =	$489.86		$516.5359	$516.54	$516.55	$516.60