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	$186.54	3.379%	$192.8432	$192.84	$192.85	$192.80
Purchase #2	$82.99	4.211%	$86.4847	$86.48	$86.50	$86.50
Purchase #3	$22.95	13.764%	$26.1088	$26.11	$26.10	$26.10
Purchase #4	$108.46	4.703%	$113.5609	$113.56	$113.55	$113.60
Purchase #5	$212.25	5.549%	$224.0278	$224.03	$224.05	$224.00
Purchase #6	$231.96	10.155%	$255.5155	$255.52	$255.50	$255.50
Purchase #7	$99.56	11.538%	$111.0472	$111.05	$111.05	$111.00
7 purchase totals =	$944.71		$1,009.5881	$1,009.59	$1,009.60	$1,009.50