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	$84.80	7.847%	$91.4543	$91.45	$91.45	$91.50
Purchase #2	$31.58	6.404%	$33.6024	$33.60	$33.60	$33.60
Purchase #3	$140.28	4.524%	$146.6263	$146.63	$146.65	$146.60
Purchase #4	$66.71	8.837%	$72.6052	$72.61	$72.60	$72.60
Purchase #5	$249.59	9.272%	$272.732	$272.73	$272.75	$272.70
Purchase #6	$161.91	12.452%	$182.071	$182.07	$182.05	$182.10
Purchase #7	$105.65	8.761%	$114.906	$114.91	$114.90	$114.90
7 purchase totals =	$840.52		$913.9972	$914.00	$914.00	$914.00