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	$113.51	3.123%	$117.0549	$117.05	$117.05	$117.10
Purchase #2	$107.34	11.621%	$119.814	$119.81	$119.80	$119.80
Purchase #3	$137.65	3.786%	$142.8614	$142.86	$142.85	$142.90
Purchase #4	$216.90	8.830%	$236.0523	$236.05	$236.05	$236.10
Purchase #5	$133.76	4.585%	$139.8929	$139.89	$139.90	$139.90
Purchase #6	$65.54	11.511%	$73.0843	$73.08	$73.10	$73.10
Purchase #7	$95.51	9.418%	$104.5051	$104.51	$104.50	$104.50
7 purchase totals =	$870.21		$933.2649	$933.25	$933.25	$933.40