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	$60.81	10.572%	$67.2388	$67.24	$67.25	$67.20
Purchase #2	$84.35	11.841%	$94.3379	$94.34	$94.35	$94.30
Purchase #3	$11.40	6.690%	$12.1627	$12.16	$12.15	$12.20
Purchase #4	$168.36	8.637%	$182.9013	$182.90	$182.90	$182.90
Purchase #5	$52.41	13.314%	$59.3879	$59.39	$59.40	$59.40
Purchase #6	$50.40	9.638%	$55.2576	$55.26	$55.25	$55.30
Purchase #7	$82.96	12.120%	$93.0148	$93.01	$93.00	$93.00
7 purchase totals =	$510.69		$564.3010	$564.30	$564.30	$564.30