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	$186.25	12.334%	$209.2221	$209.22	$209.20	$209.20
Purchase #2	$242.52	4.331%	$253.0235	$253.02	$253.00	$253.00
Purchase #3	$159.64	13.659%	$181.4452	$181.45	$181.45	$181.40
Purchase #4	$35.96	7.171%	$38.5387	$38.54	$38.55	$38.50
Purchase #5	$185.99	5.466%	$196.1562	$196.16	$196.15	$196.20
Purchase #6	$132.95	7.176%	$142.4905	$142.49	$142.50	$142.50
Purchase #7	$222.46	10.138%	$245.013	$245.01	$245.00	$245.00
7 purchase totals =	$1,165.77		$1,265.8892	$1,265.89	$1,265.85	$1,265.80