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	$206.37	4.709%	$216.088	$216.09	$216.10	$216.10
Purchase #2	$63.78	10.606%	$70.5445	$70.54	$70.55	$70.50
Purchase #3	$233.70	5.438%	$246.4086	$246.41	$246.40	$246.40
Purchase #4	$196.39	9.760%	$215.5577	$215.56	$215.55	$215.60
Purchase #5	$39.88	6.704%	$42.5536	$42.55	$42.55	$42.60
Purchase #6	$111.58	4.171%	$116.234	$116.23	$116.25	$116.20
Purchase #7	$123.82	6.389%	$131.7309	$131.73	$131.75	$131.70
7 purchase totals =	$975.52		$1,039.1173	$1,039.11	$1,039.15	$1,039.10