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	$220.58	9.546%	$241.6366	$241.64	$241.65	$241.60
Purchase #2	$221.82	3.407%	$229.3774	$229.38	$229.40	$229.40
Purchase #3	$81.98	12.201%	$91.9824	$91.98	$92.00	$92.00
Purchase #4	$219.73	8.551%	$238.5191	$238.52	$238.50	$238.50
Purchase #5	$184.26	6.494%	$196.2258	$196.23	$196.25	$196.20
Purchase #6	$13.89	12.583%	$15.6378	$15.64	$15.65	$15.60
Purchase #7	$134.96	13.430%	$153.0851	$153.09	$153.10	$153.10
7 purchase totals =	$1,077.22		$1,166.4642	$1,166.48	$1,166.55	$1,166.40