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	$168.65	11.464%	$187.984	$187.98	$188.00	$188.00
Purchase #2	$126.70	5.201%	$133.2897	$133.29	$133.30	$133.30
Purchase #3	$208.95	3.380%	$216.0125	$216.01	$216.00	$216.00
Purchase #4	$32.81	5.475%	$34.6063	$34.61	$34.60	$34.60
Purchase #5	$137.60	10.862%	$152.5461	$152.55	$152.55	$152.50
Purchase #6	$242.85	12.405%	$272.9755	$272.98	$273.00	$273.00
Purchase #7	$5.61	5.188%	$5.901	$5.90	$5.90	$5.90
7 purchase totals =	$923.17		$1,003.3151	$1,003.32	$1,003.35	$1,003.30