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	$204.41	7.400%	$219.5363	$219.54	$219.55	$219.50
Purchase #2	$47.89	6.417%	$50.9631	$50.96	$50.95	$51.00
Purchase #3	$113.37	8.568%	$123.0835	$123.08	$123.10	$123.10
Purchase #4	$139.72	10.816%	$154.8321	$154.83	$154.85	$154.80
Purchase #5	$210.48	4.165%	$219.2465	$219.25	$219.25	$219.20
Purchase #6	$165.52	12.724%	$186.5808	$186.58	$186.60	$186.60
Purchase #7	$121.63	3.784%	$126.2325	$126.23	$126.25	$126.20
7 purchase totals =	$1,003.02		$1,080.4748	$1,080.47	$1,080.55	$1,080.40