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	$250.97	12.189%	$281.5607	$281.56	$281.55	$281.60
Purchase #2	$8.45	5.190%	$8.8886	$8.89	$8.90	$8.90
Purchase #3	$43.33	5.342%	$45.6447	$45.64	$45.65	$45.60
Purchase #4	$166.62	10.298%	$183.7785	$183.78	$183.80	$183.80
Purchase #5	$114.83	8.586%	$124.6893	$124.69	$124.70	$124.70
Purchase #6	$22.57	12.499%	$25.391	$25.39	$25.40	$25.40
Purchase #7	$229.57	11.308%	$255.5298	$255.53	$255.55	$255.50
7 purchase totals =	$836.34		$925.4826	$925.48	$925.55	$925.50