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	$87.87	4.610%	$91.9208	$91.92	$91.90	$91.90
Purchase #2	$63.99	10.128%	$70.4709	$70.47	$70.45	$70.50
Purchase #3	$143.97	4.474%	$150.4112	$150.41	$150.40	$150.40
Purchase #4	$114.86	7.520%	$123.4975	$123.50	$123.50	$123.50
Purchase #5	$132.97	3.240%	$137.2782	$137.28	$137.30	$137.30
Purchase #6	$174.43	3.826%	$181.1037	$181.10	$181.10	$181.10
Purchase #7	$94.34	6.403%	$100.3806	$100.38	$100.40	$100.40
7 purchase totals =	$812.43		$855.0629	$855.06	$855.05	$855.10