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	$234.84	11.469%	$261.7738	$261.77	$261.75	$261.80
Purchase #2	$101.70	11.325%	$113.2175	$113.22	$113.20	$113.20
Purchase #3	$57.98	10.871%	$64.283	$64.28	$64.30	$64.30
Purchase #4	$126.47	13.498%	$143.5409	$143.54	$143.55	$143.50
Purchase #5	$39.90	6.769%	$42.6008	$42.60	$42.60	$42.60
Purchase #6	$126.51	8.534%	$137.3064	$137.31	$137.30	$137.30
Purchase #7	$120.36	10.369%	$132.8401	$132.84	$132.85	$132.80
7 purchase totals =	$807.76		$895.5625	$895.56	$895.55	$895.50