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	$136.72	4.227%	$142.4992	$142.50	$142.50	$142.50
Purchase #2	$36.63	9.366%	$40.0608	$40.06	$40.05	$40.10
Purchase #3	$43.53	6.214%	$46.235	$46.24	$46.25	$46.20
Purchase #4	$166.94	8.374%	$180.9196	$180.92	$180.90	$180.90
Purchase #5	$185.69	6.739%	$198.2036	$198.20	$198.20	$198.20
Purchase #6	$80.61	8.393%	$87.3756	$87.38	$87.40	$87.40
Purchase #7	$59.50	4.705%	$62.2995	$62.30	$62.30	$62.30
7 purchase totals =	$709.62		$757.5933	$757.60	$757.60	$757.60