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	$217.88	4.356%	$227.3709	$227.37	$227.35	$227.40
Purchase #2	$245.98	11.451%	$274.1472	$274.15	$274.15	$274.10
Purchase #3	$122.97	11.299%	$136.8644	$136.86	$136.85	$136.90
Purchase #4	$38.96	3.850%	$40.46	$40.46	$40.45	$40.50
Purchase #5	$183.89	3.297%	$189.9529	$189.95	$189.95	$190.00
Purchase #6	$104.53	7.599%	$112.4732	$112.47	$112.45	$112.50
Purchase #7	$17.57	12.667%	$19.7956	$19.80	$19.80	$19.80
7 purchase totals =	$931.78		$1,001.0642	$1,001.06	$1,001.00	$1,001.20