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	$149.79	12.754%	$168.8942	$168.89	$168.90	$168.90
Purchase #2	$160.70	12.639%	$181.0109	$181.01	$181.00	$181.00
Purchase #3	$85.52	13.667%	$97.208	$97.21	$97.20	$97.20
Purchase #4	$134.42	5.603%	$141.9516	$141.95	$141.95	$142.00
Purchase #5	$167.52	7.392%	$179.9031	$179.90	$179.90	$179.90
Purchase #6	$159.90	13.646%	$181.72	$181.72	$181.70	$181.70
Purchase #7	$201.98	13.734%	$229.7199	$229.72	$229.70	$229.70
7 purchase totals =	$1,059.83		$1,180.4077	$1,180.40	$1,180.35	$1,180.40