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	$46.96	4.472%	$49.0601	$49.06	$49.05	$49.10
Purchase #2	$53.63	5.490%	$56.5743	$56.57	$56.55	$56.60
Purchase #3	$216.54	12.749%	$244.1467	$244.15	$244.15	$244.10
Purchase #4	$42.25	3.850%	$43.8766	$43.88	$43.90	$43.90
Purchase #5	$115.33	5.800%	$122.0191	$122.02	$122.00	$122.00
Purchase #6	$70.89	11.269%	$78.8786	$78.88	$78.90	$78.90
Purchase #7	$249.79	9.700%	$274.0196	$274.02	$274.00	$274.00
7 purchase totals =	$795.39		$868.5750	$868.58	$868.55	$868.60