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	$58.59	7.490%	$62.9784	$62.98	$63.00	$63.00
Purchase #2	$240.43	10.790%	$266.3724	$266.37	$266.35	$266.40
Purchase #3	$32.51	5.180%	$34.194	$34.19	$34.20	$34.20
Purchase #4	$124.95	9.225%	$136.4766	$136.48	$136.50	$136.50
Purchase #5	$37.88	5.803%	$40.0782	$40.08	$40.10	$40.10
Purchase #6	$38.69	9.617%	$42.4108	$42.41	$42.40	$42.40
Purchase #7	$135.37	12.205%	$151.8919	$151.89	$151.90	$151.90
7 purchase totals =	$668.42		$734.4023	$734.40	$734.45	$734.50