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	$89.47	3.393%	$92.5057	$92.51	$92.50	$92.50
Purchase #2	$62.34	10.689%	$69.0035	$69.00	$69.00	$69.00
Purchase #3	$41.96	4.309%	$43.7681	$43.77	$43.75	$43.80
Purchase #4	$185.33	12.717%	$208.8984	$208.90	$208.90	$208.90
Purchase #5	$119.83	10.204%	$132.0575	$132.06	$132.05	$132.10
Purchase #6	$228.89	11.119%	$254.3403	$254.34	$254.35	$254.30
Purchase #7	$235.59	6.138%	$250.0505	$250.05	$250.05	$250.10
7 purchase totals =	$963.41		$1,050.6240	$1,050.63	$1,050.60	$1,050.70