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	$86.98	8.362%	$94.2533	$94.25	$94.25	$94.30
Purchase #2	$196.62	12.430%	$221.0599	$221.06	$221.05	$221.10
Purchase #3	$43.90	5.765%	$46.4308	$46.43	$46.45	$46.40
Purchase #4	$99.71	12.749%	$112.422	$112.42	$112.40	$112.40
Purchase #5	$30.52	3.262%	$31.5156	$31.52	$31.50	$31.50
Purchase #6	$152.31	6.427%	$162.099	$162.10	$162.10	$162.10
Purchase #7	$153.55	13.853%	$174.8213	$174.82	$174.80	$174.80
7 purchase totals =	$763.59		$842.6019	$842.60	$842.55	$842.60