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	$155.80	7.852%	$168.0334	$168.03	$168.05	$168.00
Purchase #2	$132.53	13.559%	$150.4997	$150.50	$150.50	$150.50
Purchase #3	$82.75	8.123%	$89.4718	$89.47	$89.45	$89.50
Purchase #4	$172.49	5.819%	$182.5272	$182.53	$182.55	$182.50
Purchase #5	$160.49	8.684%	$174.427	$174.43	$174.45	$174.40
Purchase #6	$239.33	9.469%	$261.9922	$261.99	$262.00	$262.00
Purchase #7	$99.76	4.251%	$104.0008	$104.00	$104.00	$104.00
7 purchase totals =	$1,043.15		$1,130.9521	$1,130.95	$1,131.00	$1,130.90