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	$101.26	10.203%	$111.5916	$111.59	$111.60	$111.60
Purchase #2	$81.85	9.180%	$89.3638	$89.36	$89.35	$89.40
Purchase #3	$102.91	3.623%	$106.6384	$106.64	$106.65	$106.60
Purchase #4	$167.82	11.843%	$187.6949	$187.69	$187.70	$187.70
Purchase #5	$146.72	7.819%	$158.192	$158.19	$158.20	$158.20
Purchase #6	$87.51	8.480%	$94.9308	$94.93	$94.95	$94.90
Purchase #7	$45.80	3.493%	$47.3998	$47.40	$47.40	$47.40
7 purchase totals =	$733.87		$795.8113	$795.80	$795.85	$795.80