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	$63.80	12.483%	$71.7642	$71.76	$71.75	$71.80
Purchase #2	$113.34	5.223%	$119.2597	$119.26	$119.25	$119.30
Purchase #3	$157.80	6.704%	$168.3789	$168.38	$168.40	$168.40
Purchase #4	$221.96	10.310%	$244.8441	$244.84	$244.85	$244.80
Purchase #5	$40.37	7.140%	$43.2524	$43.25	$43.25	$43.30
Purchase #6	$67.86	5.729%	$71.7477	$71.75	$71.75	$71.70
Purchase #7	$125.51	11.789%	$140.3064	$140.31	$140.30	$140.30
7 purchase totals =	$790.64		$859.5534	$859.55	$859.55	$859.60