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	$211.82	4.441%	$221.2269	$221.23	$221.25	$221.20
Purchase #2	$201.71	11.699%	$225.3081	$225.31	$225.30	$225.30
Purchase #3	$138.48	13.724%	$157.485	$157.49	$157.50	$157.50
Purchase #4	$113.96	11.457%	$127.0164	$127.02	$127.00	$127.00
Purchase #5	$117.80	7.831%	$127.0249	$127.02	$127.00	$127.00
Purchase #6	$165.72	4.171%	$172.6322	$172.63	$172.65	$172.60
Purchase #7	$89.96	13.786%	$102.3619	$102.36	$102.35	$102.40
7 purchase totals =	$1,039.45		$1,133.0554	$1,133.06	$1,133.05	$1,133.00