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	$218.88	4.503%	$228.7362	$228.74	$228.75	$228.70
Purchase #2	$59.55	9.682%	$65.3156	$65.32	$65.30	$65.30
Purchase #3	$92.99	8.467%	$100.8635	$100.86	$100.85	$100.90
Purchase #4	$228.47	12.302%	$256.5764	$256.58	$256.60	$256.60
Purchase #5	$214.38	5.187%	$225.4999	$225.50	$225.50	$225.50
Purchase #6	$242.69	11.630%	$270.9148	$270.91	$270.90	$270.90
Purchase #7	$223.81	8.577%	$243.0062	$243.01	$243.00	$243.00
7 purchase totals =	$1,280.77		$1,390.9126	$1,390.92	$1,390.90	$1,390.90