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	$103.92	9.188%	$113.4682	$113.47	$113.45	$113.50
Purchase #2	$160.46	11.709%	$179.2483	$179.25	$179.25	$179.20
Purchase #3	$139.55	9.265%	$152.4793	$152.48	$152.50	$152.50
Purchase #4	$29.39	11.350%	$32.7258	$32.73	$32.75	$32.70
Purchase #5	$89.65	11.649%	$100.0933	$100.09	$100.10	$100.10
Purchase #6	$19.59	13.212%	$22.1782	$22.18	$22.20	$22.20
Purchase #7	$229.59	8.746%	$249.6699	$249.67	$249.65	$249.70
7 purchase totals =	$772.15		$849.8630	$849.87	$849.90	$849.90