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	$117.58	11.745%	$131.3898	$131.39	$131.40	$131.40
Purchase #2	$16.93	9.778%	$18.5854	$18.59	$18.60	$18.60
Purchase #3	$93.79	9.754%	$102.9383	$102.94	$102.95	$102.90
Purchase #4	$199.94	11.871%	$223.6749	$223.67	$223.65	$223.70
Purchase #5	$92.46	8.830%	$100.6242	$100.62	$100.60	$100.60
Purchase #6	$84.62	8.295%	$91.6392	$91.64	$91.65	$91.60
Purchase #7	$73.69	11.278%	$82.0008	$82.00	$82.00	$82.00
7 purchase totals =	$679.01		$750.8526	$750.85	$750.85	$750.80