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	$132.59	13.467%	$150.4459	$150.45	$150.45	$150.40
Purchase #2	$50.47	6.137%	$53.5673	$53.57	$53.55	$53.60
Purchase #3	$199.88	5.276%	$210.4257	$210.43	$210.45	$210.40
Purchase #4	$228.42	13.293%	$258.7839	$258.78	$258.80	$258.80
Purchase #5	$99.89	7.595%	$107.4766	$107.48	$107.50	$107.50
Purchase #6	$171.93	10.345%	$189.7162	$189.72	$189.70	$189.70
Purchase #7	$31.57	10.791%	$34.9767	$34.98	$35.00	$35.00
7 purchase totals =	$914.75		$1,005.3923	$1,005.41	$1,005.45	$1,005.40