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	$246.85	10.796%	$273.4999	$273.50	$273.50	$273.50
Purchase #2	$13.70	7.769%	$14.7644	$14.76	$14.75	$14.80
Purchase #3	$61.59	6.411%	$65.5385	$65.54	$65.55	$65.50
Purchase #4	$88.43	4.160%	$92.1087	$92.11	$92.10	$92.10
Purchase #5	$45.35	13.453%	$51.4509	$51.45	$51.45	$51.50
Purchase #6	$80.87	6.716%	$86.3012	$86.30	$86.30	$86.30
Purchase #7	$156.57	13.841%	$178.2409	$178.24	$178.25	$178.20
7 purchase totals =	$693.36		$761.9045	$761.90	$761.90	$761.90