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	$124.38	13.668%	$141.3803	$141.38	$141.40	$141.40
Purchase #2	$190.79	10.377%	$210.5883	$210.59	$210.60	$210.60
Purchase #3	$65.43	12.233%	$73.4341	$73.43	$73.45	$73.40
Purchase #4	$86.51	10.285%	$95.4076	$95.41	$95.40	$95.40
Purchase #5	$211.42	6.342%	$224.8283	$224.83	$224.85	$224.80
Purchase #6	$211.81	9.231%	$231.3622	$231.36	$231.35	$231.40
Purchase #7	$47.31	13.170%	$53.5407	$53.54	$53.55	$53.50
7 purchase totals =	$937.65		$1,030.5415	$1,030.54	$1,030.60	$1,030.50