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	$45.54	5.508%	$48.0483	$48.05	$48.05	$48.00
Purchase #2	$124.89	5.661%	$131.96	$131.96	$131.95	$132.00
Purchase #3	$157.78	13.146%	$178.5218	$178.52	$178.50	$178.50
Purchase #4	$223.34	7.426%	$239.9252	$239.93	$239.95	$239.90
Purchase #5	$226.49	11.839%	$253.3042	$253.30	$253.30	$253.30
Purchase #6	$126.97	12.743%	$143.1498	$143.15	$143.15	$143.10
Purchase #7	$138.72	4.185%	$144.5254	$144.53	$144.55	$144.50
7 purchase totals =	$1,043.73		$1,139.4347	$1,139.44	$1,139.45	$1,139.30