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	$190.32	3.826%	$197.6016	$197.60	$197.60	$197.60
Purchase #2	$218.28	9.703%	$239.4597	$239.46	$239.45	$239.50
Purchase #3	$95.38	6.293%	$101.3823	$101.38	$101.40	$101.40
Purchase #4	$92.45	5.273%	$97.3249	$97.32	$97.30	$97.30
Purchase #5	$41.58	10.512%	$45.9509	$45.95	$45.95	$46.00
Purchase #6	$123.56	11.270%	$137.4852	$137.49	$137.50	$137.50
Purchase #7	$165.51	12.119%	$185.5682	$185.57	$185.55	$185.60
7 purchase totals =	$927.08		$1,004.7728	$1,004.77	$1,004.75	$1,004.90