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	$33.98	5.236%	$35.7592	$35.76	$35.75	$35.80
Purchase #2	$208.35	5.334%	$219.4634	$219.46	$219.45	$219.50
Purchase #3	$84.59	11.715%	$94.4997	$94.50	$94.50	$94.50
Purchase #4	$217.48	9.245%	$237.586	$237.59	$237.60	$237.60
Purchase #5	$128.43	9.563%	$140.7118	$140.71	$140.70	$140.70
Purchase #6	$61.52	10.131%	$67.7526	$67.75	$67.75	$67.80
Purchase #7	$231.33	5.281%	$243.5465	$243.55	$243.55	$243.50
7 purchase totals =	$965.68		$1,039.3192	$1,039.32	$1,039.30	$1,039.40