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	$163.40	7.473%	$175.6109	$175.61	$175.60	$175.60
Purchase #2	$54.34	9.845%	$59.6898	$59.69	$59.70	$59.70
Purchase #3	$167.86	4.775%	$175.8753	$175.88	$175.90	$175.90
Purchase #4	$192.41	4.126%	$200.3488	$200.35	$200.35	$200.30
Purchase #5	$130.36	6.680%	$139.068	$139.07	$139.05	$139.10
Purchase #6	$79.47	10.790%	$88.0448	$88.04	$88.05	$88.00
Purchase #7	$201.59	4.638%	$210.9397	$210.94	$210.95	$210.90
7 purchase totals =	$989.43		$1,049.5773	$1,049.58	$1,049.60	$1,049.50