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	$42.47	3.322%	$43.8809	$43.88	$43.90	$43.90
Purchase #2	$21.60	7.541%	$23.2289	$23.23	$23.25	$23.20
Purchase #3	$249.70	8.279%	$270.3727	$270.37	$270.35	$270.40
Purchase #4	$63.79	13.370%	$72.3187	$72.32	$72.30	$72.30
Purchase #5	$180.60	7.225%	$193.6484	$193.65	$193.65	$193.60
Purchase #6	$175.49	11.822%	$196.2364	$196.24	$196.25	$196.20
Purchase #7	$216.47	10.248%	$238.6538	$238.65	$238.65	$238.70
7 purchase totals =	$950.12		$1,038.3398	$1,038.34	$1,038.35	$1,038.30