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	$159.47	9.351%	$174.382	$174.38	$174.40	$174.40
Purchase #2	$119.89	9.771%	$131.6045	$131.60	$131.60	$131.60
Purchase #3	$213.47	9.841%	$234.4776	$234.48	$234.50	$234.50
Purchase #4	$68.90	8.447%	$74.72	$74.72	$74.70	$74.70
Purchase #5	$61.55	6.361%	$65.4652	$65.47	$65.45	$65.50
Purchase #6	$226.66	4.184%	$236.1435	$236.14	$236.15	$236.10
Purchase #7	$80.80	7.504%	$86.8632	$86.86	$86.85	$86.90
7 purchase totals =	$930.74		$1,003.6560	$1,003.65	$1,003.65	$1,003.70