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	$209.69	11.124%	$233.0159	$233.02	$233.00	$233.00
Purchase #2	$138.58	10.227%	$152.7526	$152.75	$152.75	$152.80
Purchase #3	$200.71	8.448%	$217.666	$217.67	$217.65	$217.70
Purchase #4	$248.95	8.331%	$269.69	$269.69	$269.70	$269.70
Purchase #5	$100.58	5.161%	$105.7709	$105.77	$105.75	$105.80
Purchase #6	$69.88	12.762%	$78.7981	$78.80	$78.80	$78.80
Purchase #7	$222.80	4.602%	$233.0533	$233.05	$233.05	$233.10
7 purchase totals =	$1,191.19		$1,290.7468	$1,290.75	$1,290.70	$1,290.90