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	$175.58	11.838%	$196.3652	$196.37	$196.35	$196.40
Purchase #2	$15.62	4.382%	$16.3045	$16.30	$16.30	$16.30
Purchase #3	$82.89	3.172%	$85.5193	$85.52	$85.50	$85.50
Purchase #4	$19.95	3.145%	$20.5774	$20.58	$20.60	$20.60
Purchase #5	$165.64	5.403%	$174.5895	$174.59	$174.60	$174.60
Purchase #6	$44.57	3.474%	$46.1184	$46.12	$46.10	$46.10
Purchase #7	$136.36	3.524%	$141.1653	$141.17	$141.15	$141.20
7 purchase totals =	$640.61		$680.6396	$680.65	$680.60	$680.70