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	$213.32	13.688%	$242.5192	$242.52	$242.50	$242.50
Purchase #2	$192.35	13.508%	$218.3326	$218.33	$218.35	$218.30
Purchase #3	$211.94	9.852%	$232.8203	$232.82	$232.80	$232.80
Purchase #4	$102.51	6.818%	$109.4991	$109.50	$109.50	$109.50
Purchase #5	$73.67	11.631%	$82.2386	$82.24	$82.25	$82.20
Purchase #6	$97.79	9.120%	$106.7084	$106.71	$106.70	$106.70
Purchase #7	$145.70	4.628%	$152.443	$152.44	$152.45	$152.40
7 purchase totals =	$1,037.28		$1,144.5612	$1,144.56	$1,144.55	$1,144.40