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	$222.91	3.421%	$230.5358	$230.54	$230.55	$230.50
Purchase #2	$212.83	11.271%	$236.8181	$236.82	$236.80	$236.80
Purchase #3	$157.98	13.522%	$179.3421	$179.34	$179.35	$179.30
Purchase #4	$6.88	12.854%	$7.7644	$7.76	$7.75	$7.80
Purchase #5	$73.42	10.189%	$80.9008	$80.90	$80.90	$80.90
Purchase #6	$172.38	10.402%	$190.311	$190.31	$190.30	$190.30
Purchase #7	$201.69	3.427%	$208.6019	$208.60	$208.60	$208.60
7 purchase totals =	$1,048.09		$1,134.2741	$1,134.27	$1,134.25	$1,134.20