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	$59.96	7.661%	$64.5535	$64.55	$64.55	$64.60
Purchase #2	$42.31	7.768%	$45.5966	$45.60	$45.60	$45.60
Purchase #3	$100.66	4.679%	$105.3699	$105.37	$105.35	$105.40
Purchase #4	$139.84	7.600%	$150.4678	$150.47	$150.45	$150.50
Purchase #5	$43.36	13.292%	$49.1234	$49.12	$49.10	$49.10
Purchase #6	$14.87	7.749%	$16.0223	$16.02	$16.00	$16.00
Purchase #7	$174.55	10.289%	$192.5094	$192.51	$192.50	$192.50
7 purchase totals =	$575.55		$623.6429	$623.64	$623.55	$623.70