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	$145.46	9.754%	$159.6482	$159.65	$159.65	$159.60
Purchase #2	$200.34	12.455%	$225.2923	$225.29	$225.30	$225.30
Purchase #3	$116.76	5.567%	$123.26	$123.26	$123.25	$123.30
Purchase #4	$132.53	5.227%	$139.4573	$139.46	$139.45	$139.50
Purchase #5	$226.40	6.154%	$240.3327	$240.33	$240.35	$240.30
Purchase #6	$89.81	13.187%	$101.6532	$101.65	$101.65	$101.70
Purchase #7	$54.37	7.143%	$58.2536	$58.25	$58.25	$58.30
7 purchase totals =	$965.67		$1,047.8973	$1,047.89	$1,047.90	$1,048.00