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	$148.39	11.162%	$164.9533	$164.95	$164.95	$165.00
Purchase #2	$221.95	3.661%	$230.0756	$230.08	$230.10	$230.10
Purchase #3	$162.61	11.473%	$181.2662	$181.27	$181.25	$181.30
Purchase #4	$95.37	4.745%	$99.8953	$99.90	$99.90	$99.90
Purchase #5	$75.95	3.298%	$78.4548	$78.45	$78.45	$78.50
Purchase #6	$196.86	12.586%	$221.6368	$221.64	$221.65	$221.60
Purchase #7	$213.46	8.221%	$231.0085	$231.01	$231.00	$231.00
7 purchase totals =	$1,114.59		$1,207.2905	$1,207.30	$1,207.30	$1,207.40