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	$246.76	4.120%	$256.9265	$256.93	$256.95	$256.90
Purchase #2	$183.33	12.657%	$206.5341	$206.53	$206.55	$206.50
Purchase #3	$38.77	11.654%	$43.2883	$43.29	$43.30	$43.30
Purchase #4	$44.37	6.789%	$47.3823	$47.38	$47.40	$47.40
Purchase #5	$182.85	7.574%	$196.6991	$196.70	$196.70	$196.70
Purchase #6	$172.63	10.327%	$190.4575	$190.46	$190.45	$190.50
Purchase #7	$153.45	10.176%	$169.0651	$169.07	$169.05	$169.10
7 purchase totals =	$1,022.16		$1,110.3529	$1,110.36	$1,110.40	$1,110.40