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	$82.90	9.565%	$90.8294	$90.83	$90.85	$90.80
Purchase #2	$185.86	8.470%	$201.6023	$201.60	$201.60	$201.60
Purchase #3	$94.88	10.355%	$104.7048	$104.70	$104.70	$104.70
Purchase #4	$190.79	3.573%	$197.6069	$197.61	$197.60	$197.60
Purchase #5	$145.88	3.735%	$151.3286	$151.33	$151.35	$151.30
Purchase #6	$207.59	4.261%	$216.4354	$216.44	$216.45	$216.40
Purchase #7	$108.60	13.229%	$122.9667	$122.97	$122.95	$123.00
7 purchase totals =	$1,016.50		$1,085.4741	$1,085.48	$1,085.50	$1,085.40