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	$193.38	4.232%	$201.5638	$201.56	$201.55	$201.60
Purchase #2	$55.83	6.657%	$59.5466	$59.55	$59.55	$59.50
Purchase #3	$150.39	10.771%	$166.5885	$166.59	$166.60	$166.60
Purchase #4	$233.53	4.419%	$243.8497	$243.85	$243.85	$243.80
Purchase #5	$146.68	10.109%	$161.5079	$161.51	$161.50	$161.50
Purchase #6	$144.37	10.393%	$159.3744	$159.37	$159.35	$159.40
Purchase #7	$134.64	3.233%	$138.9929	$138.99	$139.00	$139.00
7 purchase totals =	$1,058.82		$1,131.4238	$1,131.42	$1,131.40	$1,131.40