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	$83.99	4.152%	$87.4773	$87.48	$87.50	$87.50
Purchase #2	$61.63	4.866%	$64.6289	$64.63	$64.65	$64.60
Purchase #3	$133.77	13.771%	$152.1915	$152.19	$152.20	$152.20
Purchase #4	$250.96	11.833%	$280.6561	$280.66	$280.65	$280.70
Purchase #5	$176.50	6.529%	$188.0237	$188.02	$188.00	$188.00
Purchase #6	$135.66	11.314%	$151.0086	$151.01	$151.00	$151.00
Purchase #7	$229.57	11.264%	$255.4288	$255.43	$255.45	$255.40
7 purchase totals =	$1,072.08		$1,179.4149	$1,179.42	$1,179.45	$1,179.40