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	$116.75	12.481%	$131.3216	$131.32	$131.30	$131.30
Purchase #2	$20.44	7.609%	$21.9953	$22.00	$22.00	$22.00
Purchase #3	$55.35	9.782%	$60.7643	$60.76	$60.75	$60.80
Purchase #4	$121.65	5.576%	$128.4332	$128.43	$128.45	$128.40
Purchase #5	$231.88	4.182%	$241.5772	$241.58	$241.60	$241.60
Purchase #6	$191.33	13.871%	$217.8694	$217.87	$217.85	$217.90
Purchase #7	$193.40	12.497%	$217.5692	$217.57	$217.55	$217.60
7 purchase totals =	$930.80		$1,019.5302	$1,019.53	$1,019.50	$1,019.60