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	$56.71	11.744%	$63.37	$63.37	$63.35	$63.40
Purchase #2	$238.29	7.604%	$256.4096	$256.41	$256.40	$256.40
Purchase #3	$52.31	6.269%	$55.5893	$55.59	$55.60	$55.60
Purchase #4	$85.26	3.240%	$88.0224	$88.02	$88.00	$88.00
Purchase #5	$41.69	10.190%	$45.9382	$45.94	$45.95	$45.90
Purchase #6	$93.56	4.694%	$97.9517	$97.95	$97.95	$98.00
Purchase #7	$137.63	12.103%	$154.2874	$154.29	$154.30	$154.30
7 purchase totals =	$705.45		$761.5686	$761.57	$761.55	$761.60