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	$189.68	7.774%	$204.4257	$204.43	$204.45	$204.40
Purchase #2	$91.81	12.748%	$103.5139	$103.51	$103.50	$103.50
Purchase #3	$54.41	8.460%	$59.0131	$59.01	$59.00	$59.00
Purchase #4	$227.94	7.693%	$245.4754	$245.48	$245.50	$245.50
Purchase #5	$59.87	4.280%	$62.4324	$62.43	$62.45	$62.40
Purchase #6	$13.80	7.286%	$14.8055	$14.81	$14.80	$14.80
Purchase #7	$223.33	4.710%	$233.8488	$233.85	$233.85	$233.80
7 purchase totals =	$860.84		$923.5148	$923.52	$923.55	$923.40