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	$196.85	13.693%	$223.8047	$223.80	$223.80	$223.80
Purchase #2	$226.47	3.595%	$234.6116	$234.61	$234.60	$234.60
Purchase #3	$213.30	13.752%	$242.633	$242.63	$242.65	$242.60
Purchase #4	$193.59	5.255%	$203.7632	$203.76	$203.75	$203.80
Purchase #5	$230.35	6.630%	$245.6222	$245.62	$245.60	$245.60
Purchase #6	$223.26	12.158%	$250.404	$250.40	$250.40	$250.40
Purchase #7	$100.59	8.703%	$109.3443	$109.34	$109.35	$109.30
7 purchase totals =	$1,384.41		$1,510.1830	$1,510.16	$1,510.15	$1,510.10