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	$204.96	9.643%	$224.7243	$224.72	$224.70	$224.70
Purchase #2	$192.96	10.481%	$213.1841	$213.18	$213.20	$213.20
Purchase #3	$170.72	11.795%	$190.8564	$190.86	$190.85	$190.90
Purchase #4	$191.86	9.393%	$209.8814	$209.88	$209.90	$209.90
Purchase #5	$106.63	11.685%	$119.0897	$119.09	$119.10	$119.10
Purchase #6	$67.79	7.606%	$72.9461	$72.95	$72.95	$72.90
Purchase #7	$223.64	8.457%	$242.5532	$242.55	$242.55	$242.60
7 purchase totals =	$1,158.56		$1,273.2352	$1,273.23	$1,273.25	$1,273.30