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	$219.97	11.531%	$245.3347	$245.33	$245.35	$245.30
Purchase #2	$164.70	10.175%	$181.4582	$181.46	$181.45	$181.50
Purchase #3	$126.40	12.408%	$142.0837	$142.08	$142.10	$142.10
Purchase #4	$173.79	13.122%	$196.5947	$196.59	$196.60	$196.60
Purchase #5	$9.61	7.545%	$10.3351	$10.34	$10.35	$10.30
Purchase #6	$110.81	5.371%	$116.7616	$116.76	$116.75	$116.80
Purchase #7	$211.46	9.332%	$231.1934	$231.19	$231.20	$231.20
7 purchase totals =	$1,016.74		$1,123.7614	$1,123.75	$1,123.80	$1,123.80