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	$149.46	11.130%	$166.0949	$166.09	$166.10	$166.10
Purchase #2	$66.60	8.427%	$72.2124	$72.21	$72.20	$72.20
Purchase #3	$182.47	8.646%	$198.2464	$198.25	$198.25	$198.20
Purchase #4	$188.93	4.405%	$197.2524	$197.25	$197.25	$197.30
Purchase #5	$55.67	12.492%	$62.6243	$62.62	$62.60	$62.60
Purchase #6	$100.29	9.492%	$109.8095	$109.81	$109.80	$109.80
Purchase #7	$225.68	13.380%	$255.876	$255.88	$255.90	$255.90
7 purchase totals =	$969.10		$1,062.1159	$1,062.11	$1,062.10	$1,062.10