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	$160.70	9.538%	$176.0276	$176.03	$176.05	$176.00
Purchase #2	$218.95	13.510%	$248.5301	$248.53	$248.55	$248.50
Purchase #3	$84.46	12.855%	$95.3173	$95.32	$95.30	$95.30
Purchase #4	$128.91	8.435%	$139.7836	$139.78	$139.80	$139.80
Purchase #5	$175.89	7.813%	$189.6323	$189.63	$189.65	$189.60
Purchase #6	$68.64	3.663%	$71.1543	$71.15	$71.15	$71.20
Purchase #7	$43.50	4.524%	$45.4679	$45.47	$45.45	$45.50
7 purchase totals =	$881.05		$965.9131	$965.91	$965.95	$965.90