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	$119.45	9.142%	$130.3701	$130.37	$130.35	$130.40
Purchase #2	$131.81	3.368%	$136.2494	$136.25	$136.25	$136.20
Purchase #3	$46.37	11.353%	$51.6344	$51.63	$51.65	$51.60
Purchase #4	$78.29	10.490%	$86.5026	$86.50	$86.50	$86.50
Purchase #5	$160.81	9.174%	$175.5627	$175.56	$175.55	$175.60
Purchase #6	$140.93	9.388%	$154.1605	$154.16	$154.15	$154.20
Purchase #7	$98.41	6.580%	$104.8854	$104.89	$104.90	$104.90
7 purchase totals =	$776.07		$839.3651	$839.36	$839.35	$839.40