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	$47.31	3.376%	$48.9072	$48.91	$48.90	$48.90
Purchase #2	$50.55	13.414%	$57.3308	$57.33	$57.35	$57.30
Purchase #3	$137.27	3.542%	$142.1321	$142.13	$142.15	$142.10
Purchase #4	$250.77	3.210%	$258.8197	$258.82	$258.80	$258.80
Purchase #5	$224.47	7.238%	$240.7171	$240.72	$240.70	$240.70
Purchase #6	$49.30	9.617%	$54.0412	$54.04	$54.05	$54.00
Purchase #7	$84.69	11.666%	$94.5699	$94.57	$94.55	$94.60
7 purchase totals =	$844.36		$896.5180	$896.52	$896.50	$896.40