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	$165.50	10.318%	$182.5763	$182.58	$182.60	$182.60
Purchase #2	$81.82	5.508%	$86.3266	$86.33	$86.35	$86.30
Purchase #3	$161.86	8.684%	$175.9159	$175.92	$175.90	$175.90
Purchase #4	$164.32	12.741%	$185.256	$185.26	$185.25	$185.30
Purchase #5	$240.91	13.657%	$273.8111	$273.81	$273.80	$273.80
Purchase #6	$167.41	6.300%	$177.9568	$177.96	$177.95	$178.00
Purchase #7	$111.95	6.322%	$119.0275	$119.03	$119.05	$119.00
7 purchase totals =	$1,093.77		$1,200.8702	$1,200.89	$1,200.90	$1,200.90