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	$72.95	13.542%	$82.8289	$82.83	$82.85	$82.80
Purchase #2	$82.66	13.298%	$93.6521	$93.65	$93.65	$93.70
Purchase #3	$160.85	11.864%	$179.9332	$179.93	$179.95	$179.90
Purchase #4	$28.27	4.508%	$29.5444	$29.54	$29.55	$29.50
Purchase #5	$82.30	8.299%	$89.1301	$89.13	$89.15	$89.10
Purchase #6	$175.41	4.358%	$183.0544	$183.05	$183.05	$183.10
Purchase #7	$180.57	4.603%	$188.8816	$188.88	$188.90	$188.90
7 purchase totals =	$783.01		$847.0247	$847.01	$847.10	$847.00