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	$69.86	3.133%	$72.0487	$72.05	$72.05	$72.00
Purchase #2	$80.75	11.815%	$90.2906	$90.29	$90.30	$90.30
Purchase #3	$207.25	4.727%	$217.0467	$217.05	$217.05	$217.00
Purchase #4	$184.27	6.638%	$196.5018	$196.50	$196.50	$196.50
Purchase #5	$239.60	8.637%	$260.2943	$260.29	$260.30	$260.30
Purchase #6	$108.69	6.807%	$116.0885	$116.09	$116.10	$116.10
Purchase #7	$148.67	7.311%	$159.5393	$159.54	$159.55	$159.50
7 purchase totals =	$1,039.09		$1,111.8099	$1,111.81	$1,111.85	$1,111.70