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	$241.85	8.307%	$261.9405	$261.94	$261.95	$261.90
Purchase #2	$17.95	13.330%	$20.3427	$20.34	$20.35	$20.30
Purchase #3	$140.64	3.112%	$145.0167	$145.02	$145.00	$145.00
Purchase #4	$55.73	10.457%	$61.5577	$61.56	$61.55	$61.60
Purchase #5	$139.81	3.533%	$144.7495	$144.75	$144.75	$144.70
Purchase #6	$54.81	8.837%	$59.6536	$59.65	$59.65	$59.70
Purchase #7	$152.99	12.526%	$172.1535	$172.15	$172.15	$172.20
7 purchase totals =	$803.78		$865.4142	$865.41	$865.40	$865.40