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	$143.88	8.182%	$155.6523	$155.65	$155.65	$155.70
Purchase #2	$36.85	12.623%	$41.5016	$41.50	$41.50	$41.50
Purchase #3	$109.90	13.367%	$124.5903	$124.59	$124.60	$124.60
Purchase #4	$49.61	4.662%	$51.9228	$51.92	$51.90	$51.90
Purchase #5	$130.78	13.846%	$148.8878	$148.89	$148.90	$148.90
Purchase #6	$140.79	8.238%	$152.3883	$152.39	$152.40	$152.40
Purchase #7	$33.64	7.308%	$36.0984	$36.10	$36.10	$36.10
7 purchase totals =	$645.45		$711.0415	$711.04	$711.05	$711.10