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	$74.62	11.274%	$83.0327	$83.03	$83.05	$83.00
Purchase #2	$21.66	10.798%	$23.9988	$24.00	$24.00	$24.00
Purchase #3	$6.79	10.741%	$7.5193	$7.52	$7.50	$7.50
Purchase #4	$182.73	3.184%	$188.5481	$188.55	$188.55	$188.50
Purchase #5	$144.51	6.495%	$153.8959	$153.90	$153.90	$153.90
Purchase #6	$141.56	10.533%	$156.4705	$156.47	$156.45	$156.50
Purchase #7	$83.51	5.723%	$88.2893	$88.29	$88.30	$88.30
7 purchase totals =	$655.38		$701.7546	$701.76	$701.75	$701.70