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	$236.32	3.707%	$245.0804	$245.08	$245.10	$245.10
Purchase #2	$68.89	13.585%	$78.2487	$78.25	$78.25	$78.20
Purchase #3	$42.98	3.295%	$44.3962	$44.40	$44.40	$44.40
Purchase #4	$105.42	10.612%	$116.6072	$116.61	$116.60	$116.60
Purchase #5	$225.95	5.336%	$238.0067	$238.01	$238.00	$238.00
Purchase #6	$150.36	11.420%	$167.5311	$167.53	$167.55	$167.50
Purchase #7	$136.53	10.445%	$150.7906	$150.79	$150.80	$150.80
7 purchase totals =	$966.45		$1,040.6609	$1,040.67	$1,040.70	$1,040.60