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	$194.59	7.446%	$209.0792	$209.08	$209.10	$209.10
Purchase #2	$142.42	7.334%	$152.8651	$152.87	$152.85	$152.90
Purchase #3	$160.41	3.732%	$166.3965	$166.40	$166.40	$166.40
Purchase #4	$135.25	12.812%	$152.5782	$152.58	$152.60	$152.60
Purchase #5	$221.85	3.864%	$230.4223	$230.42	$230.40	$230.40
Purchase #6	$203.93	11.553%	$227.49	$227.49	$227.50	$227.50
Purchase #7	$125.89	4.672%	$131.7716	$131.77	$131.75	$131.80
7 purchase totals =	$1,184.34		$1,270.6029	$1,270.61	$1,270.60	$1,270.70