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	$82.43	8.730%	$89.6261	$89.63	$89.65	$89.60
Purchase #2	$10.38	12.779%	$11.7065	$11.71	$11.70	$11.70
Purchase #3	$232.30	10.245%	$256.0991	$256.10	$256.10	$256.10
Purchase #4	$162.88	5.232%	$171.4019	$171.40	$171.40	$171.40
Purchase #5	$75.79	12.219%	$85.0508	$85.05	$85.05	$85.10
Purchase #6	$37.64	12.773%	$42.4478	$42.45	$42.45	$42.40
Purchase #7	$162.80	12.362%	$182.9253	$182.93	$182.95	$182.90
7 purchase totals =	$764.22		$839.2575	$839.27	$839.30	$839.20