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	$85.37	3.643%	$88.48	$88.48	$88.50	$88.50
Purchase #2	$174.71	6.775%	$186.5466	$186.55	$186.55	$186.50
Purchase #3	$184.50	11.686%	$206.0607	$206.06	$206.05	$206.10
Purchase #4	$136.27	7.529%	$146.5298	$146.53	$146.55	$146.50
Purchase #5	$187.80	5.597%	$198.3112	$198.31	$198.30	$198.30
Purchase #6	$133.64	6.656%	$142.5351	$142.54	$142.55	$142.50
Purchase #7	$65.58	3.438%	$67.8346	$67.83	$67.85	$67.80
7 purchase totals =	$967.87		$1,036.2980	$1,036.30	$1,036.35	$1,036.20