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	$214.27	8.168%	$231.7716	$231.77	$231.75	$231.80
Purchase #2	$225.30	11.341%	$250.8513	$250.85	$250.85	$250.90
Purchase #3	$90.72	8.765%	$98.6716	$98.67	$98.65	$98.70
Purchase #4	$66.37	9.704%	$72.8105	$72.81	$72.80	$72.80
Purchase #5	$51.74	10.284%	$57.0609	$57.06	$57.05	$57.10
Purchase #6	$123.63	11.547%	$137.9056	$137.91	$137.90	$137.90
Purchase #7	$196.62	7.788%	$211.9328	$211.93	$211.95	$211.90
7 purchase totals =	$968.65		$1,061.0043	$1,061.00	$1,060.95	$1,061.10