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	$234.66	5.218%	$246.9046	$246.90	$246.90	$246.90
Purchase #2	$69.73	12.562%	$78.4895	$78.49	$78.50	$78.50
Purchase #3	$5.32	7.798%	$5.7349	$5.73	$5.75	$5.70
Purchase #4	$77.64	10.617%	$85.883	$85.88	$85.90	$85.90
Purchase #5	$154.35	6.498%	$164.3797	$164.38	$164.40	$164.40
Purchase #6	$232.56	10.533%	$257.0555	$257.06	$257.05	$257.10
Purchase #7	$168.29	13.820%	$191.5477	$191.55	$191.55	$191.50
7 purchase totals =	$942.55		$1,029.9949	$1,029.99	$1,030.05	$1,030.00