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	$119.82	3.373%	$123.8615	$123.86	$123.85	$123.90
Purchase #2	$147.36	6.474%	$156.9001	$156.90	$156.90	$156.90
Purchase #3	$167.84	9.105%	$183.1218	$183.12	$183.10	$183.10
Purchase #4	$170.62	8.815%	$185.6602	$185.66	$185.65	$185.70
Purchase #5	$115.82	5.731%	$122.4576	$122.46	$122.45	$122.50
Purchase #6	$83.49	7.177%	$89.4821	$89.48	$89.50	$89.50
Purchase #7	$9.83	12.861%	$11.0942	$11.09	$11.10	$11.10
7 purchase totals =	$814.78		$872.5775	$872.57	$872.55	$872.70