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	$159.43	5.719%	$168.5478	$168.55	$168.55	$168.50
Purchase #2	$85.36	11.743%	$95.3838	$95.38	$95.40	$95.40
Purchase #3	$76.58	7.766%	$82.5272	$82.53	$82.55	$82.50
Purchase #4	$175.97	5.671%	$185.9493	$185.95	$185.95	$185.90
Purchase #5	$58.80	4.329%	$61.3455	$61.35	$61.35	$61.30
Purchase #6	$138.54	7.505%	$148.9374	$148.94	$148.95	$148.90
Purchase #7	$236.96	13.189%	$268.2127	$268.21	$268.20	$268.20
7 purchase totals =	$931.64		$1,010.9037	$1,010.91	$1,010.95	$1,010.70