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	$164.70	11.639%	$183.8694	$183.87	$183.85	$183.90
Purchase #2	$76.35	5.552%	$80.589	$80.59	$80.60	$80.60
Purchase #3	$203.82	9.103%	$222.3737	$222.37	$222.35	$222.40
Purchase #4	$5.31	12.328%	$5.9646	$5.96	$5.95	$6.00
Purchase #5	$109.58	10.755%	$121.3653	$121.37	$121.35	$121.40
Purchase #6	$182.47	4.616%	$190.8928	$190.89	$190.90	$190.90
Purchase #7	$218.70	11.379%	$243.5859	$243.59	$243.60	$243.60
7 purchase totals =	$960.93		$1,048.6407	$1,048.64	$1,048.60	$1,048.80