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	$217.93	7.276%	$233.7866	$233.79	$233.80	$233.80
Purchase #2	$235.78	5.620%	$249.0308	$249.03	$249.05	$249.00
Purchase #3	$216.86	13.266%	$245.6286	$245.63	$245.65	$245.60
Purchase #4	$126.26	8.850%	$137.434	$137.43	$137.45	$137.40
Purchase #5	$57.53	3.490%	$59.5378	$59.54	$59.55	$59.50
Purchase #6	$103.49	10.234%	$114.0812	$114.08	$114.10	$114.10
Purchase #7	$151.49	13.428%	$171.8321	$171.83	$171.85	$171.80
7 purchase totals =	$1,109.34		$1,211.3311	$1,211.33	$1,211.45	$1,211.20