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	$85.56	4.824%	$89.6874	$89.69	$89.70	$89.70
Purchase #2	$214.63	10.299%	$236.7347	$236.73	$236.75	$236.70
Purchase #3	$56.52	9.863%	$62.0946	$62.09	$62.10	$62.10
Purchase #4	$155.98	8.223%	$168.8062	$168.81	$168.80	$168.80
Purchase #5	$147.93	6.479%	$157.5144	$157.51	$157.50	$157.50
Purchase #6	$245.53	10.629%	$271.6274	$271.63	$271.65	$271.60
Purchase #7	$29.96	4.848%	$31.4125	$31.41	$31.40	$31.40
7 purchase totals =	$936.11		$1,017.8772	$1,017.87	$1,017.90	$1,017.80