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	$217.95	12.510%	$245.2155	$245.22	$245.20	$245.20
Purchase #2	$9.99	6.440%	$10.6334	$10.63	$10.65	$10.60
Purchase #3	$164.61	12.470%	$185.1369	$185.14	$185.15	$185.10
Purchase #4	$125.37	6.514%	$133.5366	$133.54	$133.55	$133.50
Purchase #5	$231.27	3.656%	$239.7252	$239.73	$239.75	$239.70
Purchase #6	$198.40	12.209%	$222.6227	$222.62	$222.60	$222.60
Purchase #7	$83.83	3.558%	$86.8127	$86.81	$86.80	$86.80
7 purchase totals =	$1,031.42		$1,123.6830	$1,123.69	$1,123.70	$1,123.50