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	$230.51	5.806%	$243.8934	$243.89	$243.90	$243.90
Purchase #2	$70.37	5.713%	$74.3902	$74.39	$74.40	$74.40
Purchase #3	$129.73	7.111%	$138.9551	$138.96	$138.95	$139.00
Purchase #4	$147.70	11.606%	$164.8421	$164.84	$164.85	$164.80
Purchase #5	$63.63	11.603%	$71.013	$71.01	$71.00	$71.00
Purchase #6	$190.67	10.450%	$210.595	$210.60	$210.60	$210.60
Purchase #7	$167.83	13.755%	$190.915	$190.92	$190.90	$190.90
7 purchase totals =	$1,000.44		$1,094.6038	$1,094.61	$1,094.60	$1,094.60