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	$197.81	12.512%	$222.56	$222.56	$222.55	$222.60
Purchase #2	$117.68	5.283%	$123.897	$123.90	$123.90	$123.90
Purchase #3	$225.42	3.248%	$232.7416	$232.74	$232.75	$232.70
Purchase #4	$78.40	13.535%	$89.0114	$89.01	$89.00	$89.00
Purchase #5	$94.81	8.150%	$102.537	$102.54	$102.55	$102.50
Purchase #6	$222.68	10.514%	$246.0926	$246.09	$246.10	$246.10
Purchase #7	$132.54	13.259%	$150.1135	$150.11	$150.10	$150.10
7 purchase totals =	$1,069.34		$1,166.9531	$1,166.95	$1,166.95	$1,166.90