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	$144.55	5.601%	$152.6462	$152.65	$152.65	$152.60
Purchase #2	$223.50	6.473%	$237.9672	$237.97	$237.95	$238.00
Purchase #3	$219.76	9.709%	$241.0965	$241.10	$241.10	$241.10
Purchase #4	$126.82	7.647%	$136.5179	$136.52	$136.50	$136.50
Purchase #5	$108.76	13.700%	$123.6601	$123.66	$123.65	$123.70
Purchase #6	$68.76	4.715%	$72.002	$72.00	$72.00	$72.00
Purchase #7	$230.59	11.220%	$256.4622	$256.46	$256.45	$256.50
7 purchase totals =	$1,122.74		$1,220.3521	$1,220.36	$1,220.30	$1,220.40