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	$88.27	4.341%	$92.1018	$92.10	$92.10	$92.10
Purchase #2	$126.31	11.313%	$140.5995	$140.60	$140.60	$140.60
Purchase #3	$157.33	7.168%	$168.6074	$168.61	$168.60	$168.60
Purchase #4	$18.86	10.578%	$20.855	$20.86	$20.85	$20.90
Purchase #5	$232.93	5.376%	$245.4523	$245.45	$245.45	$245.50
Purchase #6	$128.91	12.171%	$144.5996	$144.60	$144.60	$144.60
Purchase #7	$224.73	7.384%	$241.3241	$241.32	$241.30	$241.30
7 purchase totals =	$977.34		$1,053.5397	$1,053.54	$1,053.50	$1,053.60