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	$64.78	10.865%	$71.8183	$71.82	$71.80	$71.80
Purchase #2	$138.82	8.545%	$150.6822	$150.68	$150.70	$150.70
Purchase #3	$172.94	3.513%	$179.0154	$179.02	$179.00	$179.00
Purchase #4	$53.70	3.304%	$55.4742	$55.47	$55.45	$55.50
Purchase #5	$178.68	10.197%	$196.9	$196.90	$196.90	$196.90
Purchase #6	$112.36	10.249%	$123.8758	$123.88	$123.90	$123.90
Purchase #7	$95.46	11.680%	$106.6097	$106.61	$106.60	$106.60
7 purchase totals =	$816.74		$884.3756	$884.38	$884.35	$884.40