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	$84.28	4.470%	$88.0473	$88.05	$88.05	$88.00
Purchase #2	$249.59	12.352%	$280.4194	$280.42	$280.40	$280.40
Purchase #3	$178.36	12.487%	$200.6318	$200.63	$200.65	$200.60
Purchase #4	$95.32	10.652%	$105.4735	$105.47	$105.45	$105.50
Purchase #5	$199.36	5.670%	$210.6637	$210.66	$210.65	$210.70
Purchase #6	$208.48	7.336%	$223.7741	$223.77	$223.75	$223.80
Purchase #7	$246.98	3.437%	$255.4687	$255.47	$255.45	$255.50
7 purchase totals =	$1,262.37		$1,364.4785	$1,364.47	$1,364.40	$1,364.50