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	$176.90	10.812%	$196.0264	$196.03	$196.05	$196.00
Purchase #2	$132.90	11.591%	$148.3044	$148.30	$148.30	$148.30
Purchase #3	$16.53	3.782%	$17.1552	$17.16	$17.15	$17.20
Purchase #4	$131.96	10.353%	$145.6218	$145.62	$145.60	$145.60
Purchase #5	$152.43	3.806%	$158.2315	$158.23	$158.25	$158.20
Purchase #6	$240.67	6.524%	$256.3713	$256.37	$256.35	$256.40
Purchase #7	$6.98	11.732%	$7.7989	$7.80	$7.80	$7.80
7 purchase totals =	$858.37		$929.5095	$929.51	$929.50	$929.50