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	$188.96	3.733%	$196.0139	$196.01	$196.00	$196.00
Purchase #2	$238.40	5.150%	$250.6776	$250.68	$250.70	$250.70
Purchase #3	$36.38	5.720%	$38.4609	$38.46	$38.45	$38.50
Purchase #4	$125.52	13.429%	$142.3761	$142.38	$142.40	$142.40
Purchase #5	$134.31	10.609%	$148.5589	$148.56	$148.55	$148.60
Purchase #6	$231.34	5.696%	$244.5171	$244.52	$244.50	$244.50
Purchase #7	$239.75	8.449%	$260.0065	$260.01	$260.00	$260.00
7 purchase totals =	$1,194.66		$1,280.6110	$1,280.62	$1,280.60	$1,280.70