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	$179.79	12.807%	$202.8157	$202.82	$202.80	$202.80
Purchase #2	$67.68	5.690%	$71.531	$71.53	$71.55	$71.50
Purchase #3	$72.78	8.391%	$78.887	$78.89	$78.90	$78.90
Purchase #4	$64.68	5.807%	$68.436	$68.44	$68.45	$68.40
Purchase #5	$156.38	3.767%	$162.2708	$162.27	$162.25	$162.30
Purchase #6	$228.78	12.172%	$256.6271	$256.63	$256.65	$256.60
Purchase #7	$130.32	8.670%	$141.6187	$141.62	$141.60	$141.60
7 purchase totals =	$900.41		$982.1863	$982.20	$982.20	$982.10