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	$206.37	10.139%	$227.2939	$227.29	$227.30	$227.30
Purchase #2	$225.71	3.869%	$234.4427	$234.44	$234.45	$234.40
Purchase #3	$131.59	12.307%	$147.7848	$147.78	$147.80	$147.80
Purchase #4	$43.37	9.392%	$47.4433	$47.44	$47.45	$47.40
Purchase #5	$160.55	6.797%	$171.4626	$171.46	$171.45	$171.50
Purchase #6	$24.92	11.865%	$27.8768	$27.88	$27.90	$27.90
Purchase #7	$134.56	10.409%	$148.5664	$148.57	$148.55	$148.60
7 purchase totals =	$927.07		$1,004.8705	$1,004.86	$1,004.90	$1,004.90