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	$168.76	4.781%	$176.8284	$176.83	$176.85	$176.80
Purchase #2	$196.46	11.227%	$218.5166	$218.52	$218.50	$218.50
Purchase #3	$177.78	10.778%	$196.9411	$196.94	$196.95	$196.90
Purchase #4	$99.53	10.604%	$110.0842	$110.08	$110.10	$110.10
Purchase #5	$239.47	3.290%	$247.3486	$247.35	$247.35	$247.30
Purchase #6	$72.86	13.619%	$82.7828	$82.78	$82.80	$82.80
Purchase #7	$76.58	7.183%	$82.0807	$82.08	$82.10	$82.10
7 purchase totals =	$1,031.44		$1,114.5824	$1,114.58	$1,114.65	$1,114.50