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	$168.86	6.408%	$179.6805	$179.68	$179.70	$179.70
Purchase #2	$129.66	7.374%	$139.2211	$139.22	$139.20	$139.20
Purchase #3	$59.94	7.722%	$64.5686	$64.57	$64.55	$64.60
Purchase #4	$179.85	6.138%	$190.8892	$190.89	$190.90	$190.90
Purchase #5	$165.32	4.423%	$172.6321	$172.63	$172.65	$172.60
Purchase #6	$165.97	11.734%	$185.4449	$185.44	$185.45	$185.40
Purchase #7	$138.78	12.390%	$155.9748	$155.97	$155.95	$156.00
7 purchase totals =	$1,008.38		$1,088.4112	$1,088.40	$1,088.40	$1,088.40