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	$155.35	10.389%	$171.4893	$171.49	$171.50	$171.50
Purchase #2	$244.68	5.362%	$257.7997	$257.80	$257.80	$257.80
Purchase #3	$131.84	11.144%	$146.5322	$146.53	$146.55	$146.50
Purchase #4	$200.85	6.247%	$213.3971	$213.40	$213.40	$213.40
Purchase #5	$187.51	11.868%	$209.7637	$209.76	$209.75	$209.80
Purchase #6	$113.82	11.450%	$126.8524	$126.85	$126.85	$126.90
Purchase #7	$39.43	10.468%	$43.5575	$43.56	$43.55	$43.60
7 purchase totals =	$1,073.48		$1,169.3919	$1,169.39	$1,169.40	$1,169.50