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	$133.55	11.409%	$148.7867	$148.79	$148.80	$148.80
Purchase #2	$115.86	9.313%	$126.65	$126.65	$126.65	$126.70
Purchase #3	$250.29	12.210%	$280.8504	$280.85	$280.85	$280.90
Purchase #4	$38.80	11.503%	$43.2632	$43.26	$43.25	$43.30
Purchase #5	$85.46	5.229%	$89.9287	$89.93	$89.95	$89.90
Purchase #6	$94.37	11.648%	$105.3622	$105.36	$105.35	$105.40
Purchase #7	$137.97	6.181%	$146.4979	$146.50	$146.50	$146.50
7 purchase totals =	$856.30		$941.3391	$941.34	$941.35	$941.50