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	$55.40	6.550%	$59.0287	$59.03	$59.05	$59.00
Purchase #2	$208.64	11.160%	$231.9242	$231.92	$231.90	$231.90
Purchase #3	$31.44	7.509%	$33.8008	$33.80	$33.80	$33.80
Purchase #4	$150.71	12.416%	$169.4222	$169.42	$169.40	$169.40
Purchase #5	$76.43	3.141%	$78.8307	$78.83	$78.85	$78.80
Purchase #6	$179.80	12.507%	$202.2876	$202.29	$202.30	$202.30
Purchase #7	$245.76	6.224%	$261.0561	$261.06	$261.05	$261.10
7 purchase totals =	$948.18		$1,036.3503	$1,036.35	$1,036.35	$1,036.30