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	$54.83	7.559%	$58.9746	$58.97	$58.95	$59.00
Purchase #2	$200.88	11.442%	$223.8647	$223.86	$223.85	$223.90
Purchase #3	$41.38	4.773%	$43.3551	$43.36	$43.35	$43.40
Purchase #4	$88.43	8.863%	$96.2676	$96.27	$96.25	$96.30
Purchase #5	$13.35	13.304%	$15.1261	$15.13	$15.15	$15.10
Purchase #6	$59.98	7.508%	$64.4833	$64.48	$64.50	$64.50
Purchase #7	$100.89	7.405%	$108.3609	$108.36	$108.35	$108.40
7 purchase totals =	$559.74		$610.4323	$610.43	$610.40	$610.60