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	$233.35	7.861%	$251.6936	$251.69	$251.70	$251.70
Purchase #2	$136.75	12.104%	$153.3022	$153.30	$153.30	$153.30
Purchase #3	$246.76	13.675%	$280.5044	$280.50	$280.50	$280.50
Purchase #4	$63.67	12.582%	$71.681	$71.68	$71.70	$71.70
Purchase #5	$59.95	10.799%	$66.424	$66.42	$66.40	$66.40
Purchase #6	$83.95	8.782%	$91.3225	$91.32	$91.30	$91.30
Purchase #7	$240.68	13.635%	$273.4967	$273.50	$273.50	$273.50
7 purchase totals =	$1,065.11		$1,188.4244	$1,188.41	$1,188.40	$1,188.40