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	$125.86	12.805%	$141.9764	$141.98	$142.00	$142.00
Purchase #2	$130.51	4.666%	$136.5996	$136.60	$136.60	$136.60
Purchase #3	$158.75	12.453%	$178.5191	$178.52	$178.50	$178.50
Purchase #4	$245.83	5.166%	$258.5296	$258.53	$258.55	$258.50
Purchase #5	$229.42	13.272%	$259.8686	$259.87	$259.85	$259.90
Purchase #6	$138.52	13.260%	$156.8878	$156.89	$156.90	$156.90
Purchase #7	$175.52	13.548%	$199.2994	$199.30	$199.30	$199.30
7 purchase totals =	$1,204.41		$1,331.6805	$1,331.69	$1,331.70	$1,331.70