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	$46.76	12.473%	$52.5924	$52.59	$52.60	$52.60
Purchase #2	$233.54	11.331%	$260.0024	$260.00	$260.00	$260.00
Purchase #3	$161.84	12.776%	$182.5167	$182.52	$182.50	$182.50
Purchase #4	$99.49	12.186%	$111.6139	$111.61	$111.60	$111.60
Purchase #5	$196.45	8.338%	$212.83	$212.83	$212.85	$212.80
Purchase #6	$229.34	9.238%	$250.5264	$250.53	$250.55	$250.50
Purchase #7	$204.34	10.165%	$225.1112	$225.11	$225.10	$225.10
7 purchase totals =	$1,171.76		$1,295.1930	$1,295.19	$1,295.20	$1,295.10