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	$227.49	10.481%	$251.3332	$251.33	$251.35	$251.30
Purchase #2	$52.40	5.228%	$55.1395	$55.14	$55.15	$55.10
Purchase #3	$233.52	12.807%	$263.4269	$263.43	$263.45	$263.40
Purchase #4	$172.37	4.367%	$179.8974	$179.90	$179.90	$179.90
Purchase #5	$176.69	11.484%	$196.9811	$196.98	$197.00	$197.00
Purchase #6	$228.56	5.795%	$241.8051	$241.81	$241.80	$241.80
Purchase #7	$106.79	12.153%	$119.7682	$119.77	$119.75	$119.80
7 purchase totals =	$1,197.82		$1,308.3514	$1,308.36	$1,308.40	$1,308.30