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	$138.25	9.358%	$151.1874	$151.19	$151.20	$151.20
Purchase #2	$205.37	5.486%	$216.6366	$216.64	$216.65	$216.60
Purchase #3	$79.81	13.682%	$90.7296	$90.73	$90.75	$90.70
Purchase #4	$190.38	3.215%	$196.5007	$196.50	$196.50	$196.50
Purchase #5	$74.48	10.615%	$82.3861	$82.39	$82.40	$82.40
Purchase #6	$243.49	7.181%	$260.975	$260.98	$261.00	$261.00
Purchase #7	$62.63	5.275%	$65.9337	$65.93	$65.95	$65.90
7 purchase totals =	$994.41		$1,064.3491	$1,064.36	$1,064.45	$1,064.30