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	$111.64	4.572%	$116.7442	$116.74	$116.75	$116.70
Purchase #2	$220.47	6.859%	$235.592	$235.59	$235.60	$235.60
Purchase #3	$65.36	10.508%	$72.228	$72.23	$72.25	$72.20
Purchase #4	$44.32	10.283%	$48.8774	$48.88	$48.90	$48.90
Purchase #5	$35.67	7.566%	$38.3688	$38.37	$38.35	$38.40
Purchase #6	$232.38	12.389%	$261.1696	$261.17	$261.15	$261.20
Purchase #7	$168.33	10.119%	$185.3633	$185.36	$185.35	$185.40
7 purchase totals =	$878.17		$958.3433	$958.34	$958.35	$958.40