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	$208.34	5.326%	$219.4362	$219.44	$219.45	$219.40
Purchase #2	$125.51	13.839%	$142.8793	$142.88	$142.90	$142.90
Purchase #3	$124.47	10.839%	$137.9613	$137.96	$137.95	$138.00
Purchase #4	$86.39	3.490%	$89.405	$89.41	$89.40	$89.40
Purchase #5	$241.93	12.341%	$271.7866	$271.79	$271.80	$271.80
Purchase #6	$110.71	10.507%	$122.3423	$122.34	$122.35	$122.30
Purchase #7	$103.28	8.727%	$112.2932	$112.29	$112.30	$112.30
7 purchase totals =	$1,000.63		$1,096.1039	$1,096.11	$1,096.15	$1,096.10