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	$194.51	7.273%	$208.6567	$208.66	$208.65	$208.70
Purchase #2	$232.89	10.334%	$256.9569	$256.96	$256.95	$257.00
Purchase #3	$221.64	11.492%	$247.1109	$247.11	$247.10	$247.10
Purchase #4	$112.37	13.811%	$127.8894	$127.89	$127.90	$127.90
Purchase #5	$33.39	12.208%	$37.4663	$37.47	$37.45	$37.50
Purchase #6	$79.38	11.677%	$88.6492	$88.65	$88.65	$88.60
Purchase #7	$229.64	7.107%	$245.9605	$245.96	$245.95	$246.00
7 purchase totals =	$1,103.82		$1,212.6899	$1,212.70	$1,212.65	$1,212.80