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	$44.51	9.169%	$48.5911	$48.59	$48.60	$48.60
Purchase #2	$76.75	7.165%	$82.2491	$82.25	$82.25	$82.20
Purchase #3	$198.59	9.682%	$217.8175	$217.82	$217.80	$217.80
Purchase #4	$27.74	11.839%	$31.0241	$31.02	$31.00	$31.00
Purchase #5	$192.38	6.118%	$204.1498	$204.15	$204.15	$204.10
Purchase #6	$92.78	13.672%	$105.4649	$105.46	$105.45	$105.50
Purchase #7	$173.29	7.375%	$186.0701	$186.07	$186.05	$186.10
7 purchase totals =	$806.04		$875.3666	$875.36	$875.30	$875.30