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	$227.73	4.871%	$238.8227	$238.82	$238.80	$238.80
Purchase #2	$59.92	12.736%	$67.5514	$67.55	$67.55	$67.60
Purchase #3	$236.83	9.517%	$259.3691	$259.37	$259.35	$259.40
Purchase #4	$165.26	9.828%	$181.5018	$181.50	$181.50	$181.50
Purchase #5	$153.81	12.190%	$172.5594	$172.56	$172.55	$172.60
Purchase #6	$88.73	8.105%	$95.9216	$95.92	$95.90	$95.90
Purchase #7	$249.46	11.334%	$277.7338	$277.73	$277.75	$277.70
7 purchase totals =	$1,181.74		$1,293.4598	$1,293.45	$1,293.40	$1,293.50