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	$202.80	8.334%	$219.7014	$219.70	$219.70	$219.70
Purchase #2	$158.30	5.835%	$167.5368	$167.54	$167.55	$167.50
Purchase #3	$52.27	13.673%	$59.4169	$59.42	$59.40	$59.40
Purchase #4	$231.86	4.377%	$242.0085	$242.01	$242.00	$242.00
Purchase #5	$37.27	9.366%	$40.7607	$40.76	$40.75	$40.80
Purchase #6	$127.81	7.524%	$137.4264	$137.43	$137.45	$137.40
Purchase #7	$80.78	7.471%	$86.8151	$86.82	$86.80	$86.80
7 purchase totals =	$891.09		$953.6658	$953.68	$953.65	$953.60