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	$179.28	9.450%	$196.222	$196.22	$196.20	$196.20
Purchase #2	$115.57	13.383%	$131.0367	$131.04	$131.05	$131.00
Purchase #3	$158.83	12.607%	$178.8537	$178.85	$178.85	$178.90
Purchase #4	$138.78	8.561%	$150.661	$150.66	$150.65	$150.70
Purchase #5	$143.76	4.677%	$150.4837	$150.48	$150.50	$150.50
Purchase #6	$165.56	13.518%	$187.9404	$187.94	$187.95	$187.90
Purchase #7	$214.59	13.543%	$243.6519	$243.65	$243.65	$243.70
7 purchase totals =	$1,116.37		$1,238.8494	$1,238.84	$1,238.85	$1,238.90