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	$81.73	11.587%	$91.2001	$91.20	$91.20	$91.20
Purchase #2	$108.53	4.770%	$113.7069	$113.71	$113.70	$113.70
Purchase #3	$161.41	3.179%	$166.5412	$166.54	$166.55	$166.50
Purchase #4	$178.45	4.665%	$186.7747	$186.77	$186.75	$186.80
Purchase #5	$187.94	13.518%	$213.3457	$213.35	$213.35	$213.30
Purchase #6	$184.41	12.857%	$208.1196	$208.12	$208.10	$208.10
Purchase #7	$195.84	10.763%	$216.9183	$216.92	$216.90	$216.90
7 purchase totals =	$1,098.31		$1,196.6065	$1,196.61	$1,196.55	$1,196.50