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	$164.38	3.175%	$169.5991	$169.60	$169.60	$169.60
Purchase #2	$236.56	9.628%	$259.336	$259.34	$259.35	$259.30
Purchase #3	$147.68	5.818%	$156.272	$156.27	$156.25	$156.30
Purchase #4	$85.85	3.617%	$88.9552	$88.96	$88.95	$89.00
Purchase #5	$97.75	8.732%	$106.2855	$106.29	$106.30	$106.30
Purchase #6	$199.51	7.178%	$213.8308	$213.83	$213.85	$213.80
Purchase #7	$118.38	4.402%	$123.5911	$123.59	$123.60	$123.60
7 purchase totals =	$1,050.11		$1,117.8697	$1,117.88	$1,117.90	$1,117.90