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	$198.53	9.550%	$217.4896	$217.49	$217.50	$217.50
Purchase #2	$147.65	11.559%	$164.7169	$164.72	$164.70	$164.70
Purchase #3	$101.31	10.695%	$112.1451	$112.15	$112.15	$112.10
Purchase #4	$196.81	3.627%	$203.9483	$203.95	$203.95	$203.90
Purchase #5	$89.43	5.688%	$94.5168	$94.52	$94.50	$94.50
Purchase #6	$37.34	3.726%	$38.7313	$38.73	$38.75	$38.70
Purchase #7	$103.30	7.841%	$111.3998	$111.40	$111.40	$111.40
7 purchase totals =	$874.37		$942.9478	$942.96	$942.95	$942.80