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	$105.73	10.284%	$116.6033	$116.60	$116.60	$116.60
Purchase #2	$212.86	4.255%	$221.9172	$221.92	$221.90	$221.90
Purchase #3	$188.99	6.299%	$200.8945	$200.89	$200.90	$200.90
Purchase #4	$104.97	13.390%	$119.0255	$119.03	$119.05	$119.00
Purchase #5	$137.59	10.603%	$152.1787	$152.18	$152.20	$152.20
Purchase #6	$109.59	4.569%	$114.5972	$114.60	$114.60	$114.60
Purchase #7	$23.34	5.129%	$24.5371	$24.54	$24.55	$24.50
7 purchase totals =	$883.07		$949.7535	$949.76	$949.80	$949.70