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	$241.84	5.230%	$254.4882	$254.49	$254.50	$254.50
Purchase #2	$64.30	10.710%	$71.1865	$71.19	$71.20	$71.20
Purchase #3	$91.95	6.588%	$98.0077	$98.01	$98.00	$98.00
Purchase #4	$83.78	12.834%	$94.5323	$94.53	$94.55	$94.50
Purchase #5	$63.35	13.362%	$71.8148	$71.81	$71.80	$71.80
Purchase #6	$131.51	10.102%	$144.7951	$144.80	$144.80	$144.80
Purchase #7	$248.94	6.814%	$265.9028	$265.90	$265.90	$265.90
7 purchase totals =	$925.67		$1,000.7274	$1,000.73	$1,000.75	$1,000.70