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	$203.63	8.159%	$220.2442	$220.24	$220.25	$220.20
Purchase #2	$204.37	5.682%	$215.9823	$215.98	$216.00	$216.00
Purchase #3	$216.67	3.214%	$223.6338	$223.63	$223.65	$223.60
Purchase #4	$72.43	13.447%	$82.1697	$82.17	$82.15	$82.20
Purchase #5	$38.80	10.177%	$42.7487	$42.75	$42.75	$42.70
Purchase #6	$31.86	11.714%	$35.5921	$35.59	$35.60	$35.60
Purchase #7	$245.60	4.260%	$256.0626	$256.06	$256.05	$256.10
7 purchase totals =	$1,013.36		$1,076.4334	$1,076.42	$1,076.45	$1,076.40