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	$220.40	10.870%	$244.3575	$244.36	$244.35	$244.40
Purchase #2	$152.29	13.762%	$173.2481	$173.25	$173.25	$173.20
Purchase #3	$95.28	5.815%	$100.8205	$100.82	$100.80	$100.80
Purchase #4	$242.98	4.631%	$254.2324	$254.23	$254.25	$254.20
Purchase #5	$227.78	4.313%	$237.6042	$237.60	$237.60	$237.60
Purchase #6	$94.40	6.280%	$100.3283	$100.33	$100.35	$100.30
Purchase #7	$227.48	8.113%	$245.9355	$245.94	$245.95	$245.90
7 purchase totals =	$1,260.61		$1,356.5265	$1,356.53	$1,356.55	$1,356.40