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	$210.49	11.415%	$234.5174	$234.52	$234.50	$234.50
Purchase #2	$178.95	6.462%	$190.5137	$190.51	$190.50	$190.50
Purchase #3	$42.34	7.256%	$45.4122	$45.41	$45.40	$45.40
Purchase #4	$85.63	9.263%	$93.5619	$93.56	$93.55	$93.60
Purchase #5	$240.42	6.665%	$256.444	$256.44	$256.45	$256.40
Purchase #6	$120.99	9.801%	$132.8482	$132.85	$132.85	$132.80
Purchase #7	$80.44	6.416%	$85.601	$85.60	$85.60	$85.60
7 purchase totals =	$959.26		$1,038.8984	$1,038.89	$1,038.85	$1,038.80