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	$196.75	11.673%	$219.7166	$219.72	$219.70	$219.70
Purchase #2	$159.55	6.845%	$170.4712	$170.47	$170.45	$170.50
Purchase #3	$78.66	8.136%	$85.0598	$85.06	$85.05	$85.10
Purchase #4	$223.95	5.474%	$236.209	$236.21	$236.20	$236.20
Purchase #5	$172.51	8.330%	$186.8801	$186.88	$186.90	$186.90
Purchase #6	$106.32	10.501%	$117.4847	$117.48	$117.50	$117.50
Purchase #7	$66.30	8.767%	$72.1125	$72.11	$72.10	$72.10
7 purchase totals =	$1,004.04		$1,087.9339	$1,087.93	$1,087.90	$1,088.00