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	$136.52	10.552%	$150.9256	$150.93	$150.95	$150.90
Purchase #2	$112.27	10.152%	$123.6677	$123.67	$123.65	$123.70
Purchase #3	$40.84	11.807%	$45.662	$45.66	$45.65	$45.70
Purchase #4	$229.57	5.504%	$242.2055	$242.21	$242.20	$242.20
Purchase #5	$250.74	11.757%	$280.2195	$280.22	$280.20	$280.20
Purchase #6	$111.90	9.517%	$122.5495	$122.55	$122.55	$122.50
Purchase #7	$168.45	13.580%	$191.3255	$191.33	$191.35	$191.30
7 purchase totals =	$1,050.29		$1,156.5553	$1,156.57	$1,156.55	$1,156.50