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	$190.26	12.136%	$213.35	$213.35	$213.35	$213.40
Purchase #2	$111.39	4.281%	$116.1586	$116.16	$116.15	$116.20
Purchase #3	$57.84	8.681%	$62.8611	$62.86	$62.85	$62.90
Purchase #4	$144.63	4.477%	$151.1051	$151.11	$151.10	$151.10
Purchase #5	$223.45	3.737%	$231.8003	$231.80	$231.80	$231.80
Purchase #6	$241.34	13.165%	$273.1124	$273.11	$273.10	$273.10
Purchase #7	$151.52	7.522%	$162.9173	$162.92	$162.90	$162.90
7 purchase totals =	$1,120.43		$1,211.3048	$1,211.31	$1,211.25	$1,211.40