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	$126.42	12.617%	$142.3704	$142.37	$142.35	$142.40
Purchase #2	$83.58	3.259%	$86.3039	$86.30	$86.30	$86.30
Purchase #3	$171.27	5.626%	$180.9057	$180.91	$180.90	$180.90
Purchase #4	$224.39	7.611%	$241.4683	$241.47	$241.45	$241.50
Purchase #5	$151.53	4.111%	$157.7594	$157.76	$157.75	$157.80
Purchase #6	$162.66	3.529%	$168.4003	$168.40	$168.40	$168.40
Purchase #7	$176.75	3.498%	$182.9327	$182.93	$182.95	$182.90
7 purchase totals =	$1,096.60		$1,160.1407	$1,160.14	$1,160.10	$1,160.20