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	$54.53	8.120%	$58.9578	$58.96	$58.95	$59.00
Purchase #2	$89.60	11.750%	$100.128	$100.13	$100.15	$100.10
Purchase #3	$123.31	12.219%	$138.3772	$138.38	$138.40	$138.40
Purchase #4	$82.44	9.119%	$89.9577	$89.96	$89.95	$90.00
Purchase #5	$36.92	5.837%	$39.075	$39.08	$39.10	$39.10
Purchase #6	$24.29	11.324%	$27.0406	$27.04	$27.05	$27.00
Purchase #7	$110.75	12.225%	$124.2892	$124.29	$124.30	$124.30
7 purchase totals =	$521.84		$577.8255	$577.84	$577.90	$577.90