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	$127.27	12.810%	$143.5733	$143.57	$143.55	$143.60
Purchase #2	$202.65	8.205%	$219.2774	$219.28	$219.30	$219.30
Purchase #3	$33.69	11.846%	$37.6809	$37.68	$37.70	$37.70
Purchase #4	$201.27	11.765%	$224.9494	$224.95	$224.95	$224.90
Purchase #5	$81.70	4.600%	$85.4582	$85.46	$85.45	$85.50
Purchase #6	$179.50	6.121%	$190.4872	$190.49	$190.50	$190.50
Purchase #7	$101.61	10.704%	$112.4863	$112.49	$112.50	$112.50
7 purchase totals =	$927.69		$1,013.9127	$1,013.92	$1,013.95	$1,014.00