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	$97.60	8.477%	$105.8736	$105.87	$105.85	$105.90
Purchase #2	$160.60	4.628%	$168.0326	$168.03	$168.05	$168.00
Purchase #3	$212.46	4.481%	$221.9803	$221.98	$222.00	$222.00
Purchase #4	$210.90	5.392%	$222.2717	$222.27	$222.25	$222.30
Purchase #5	$58.34	3.467%	$60.3626	$60.36	$60.35	$60.40
Purchase #6	$67.93	13.301%	$76.9654	$76.97	$76.95	$77.00
Purchase #7	$74.89	4.695%	$78.4061	$78.41	$78.40	$78.40
7 purchase totals =	$882.72		$933.8923	$933.89	$933.85	$934.00