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	$223.56	9.539%	$244.8854	$244.89	$244.90	$244.90
Purchase #2	$227.47	13.706%	$258.647	$258.65	$258.65	$258.60
Purchase #3	$203.44	13.653%	$231.2157	$231.22	$231.20	$231.20
Purchase #4	$80.80	3.187%	$83.3751	$83.38	$83.40	$83.40
Purchase #5	$110.43	11.781%	$123.4398	$123.44	$123.45	$123.40
Purchase #6	$87.59	11.724%	$97.8591	$97.86	$97.85	$97.90
Purchase #7	$50.53	8.127%	$54.6366	$54.64	$54.65	$54.60
7 purchase totals =	$983.82		$1,094.0587	$1,094.08	$1,094.10	$1,094.00