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	$132.91	8.709%	$144.4851	$144.49	$144.50	$144.50
Purchase #2	$28.44	10.255%	$31.3565	$31.36	$31.35	$31.40
Purchase #3	$20.79	9.152%	$22.6927	$22.69	$22.70	$22.70
Purchase #4	$38.81	10.816%	$43.0077	$43.01	$43.00	$43.00
Purchase #5	$114.27	7.807%	$123.1911	$123.19	$123.20	$123.20
Purchase #6	$132.35	13.632%	$150.392	$150.39	$150.40	$150.40
Purchase #7	$233.29	5.244%	$245.5237	$245.52	$245.50	$245.50
7 purchase totals =	$700.86		$760.6488	$760.65	$760.65	$760.70