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	$194.32	3.247%	$200.6296	$200.63	$200.65	$200.60
Purchase #2	$28.87	10.400%	$31.8725	$31.87	$31.85	$31.90
Purchase #3	$226.94	10.744%	$251.3224	$251.32	$251.30	$251.30
Purchase #4	$79.83	12.791%	$90.0411	$90.04	$90.05	$90.00
Purchase #5	$31.82	3.873%	$33.0524	$33.05	$33.05	$33.10
Purchase #6	$12.86	10.426%	$14.2008	$14.20	$14.20	$14.20
Purchase #7	$227.72	10.189%	$250.9224	$250.92	$250.90	$250.90
7 purchase totals =	$802.36		$872.0412	$872.03	$872.00	$872.00