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	$58.48	12.213%	$65.6222	$65.62	$65.60	$65.60
Purchase #2	$150.42	11.732%	$168.0673	$168.07	$168.05	$168.10
Purchase #3	$52.64	11.386%	$58.6336	$58.63	$58.65	$58.60
Purchase #4	$62.86	6.672%	$67.054	$67.05	$67.05	$67.10
Purchase #5	$63.89	5.755%	$67.5669	$67.57	$67.55	$67.60
Purchase #6	$203.68	7.169%	$218.2818	$218.28	$218.30	$218.30
Purchase #7	$186.72	10.230%	$205.8215	$205.82	$205.80	$205.80
7 purchase totals =	$778.69		$851.0473	$851.04	$851.00	$851.10