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	$32.38	13.453%	$36.7361	$36.74	$36.75	$36.70
Purchase #2	$219.66	3.105%	$226.4804	$226.48	$226.50	$226.50
Purchase #3	$211.77	5.500%	$223.4174	$223.42	$223.40	$223.40
Purchase #4	$245.54	8.742%	$267.0051	$267.01	$267.00	$267.00
Purchase #5	$190.42	11.307%	$211.9508	$211.95	$211.95	$212.00
Purchase #6	$101.72	3.697%	$105.4806	$105.48	$105.50	$105.50
Purchase #7	$30.78	10.209%	$33.9223	$33.92	$33.90	$33.90
7 purchase totals =	$1,032.27		$1,104.9927	$1,105.00	$1,105.00	$1,105.00