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	$43.32	10.148%	$47.7161	$47.72	$47.70	$47.70
Purchase #2	$237.86	3.271%	$245.6404	$245.64	$245.65	$245.60
Purchase #3	$12.46	3.369%	$12.8798	$12.88	$12.90	$12.90
Purchase #4	$250.60	9.762%	$275.0636	$275.06	$275.05	$275.10
Purchase #5	$104.84	8.181%	$113.417	$113.42	$113.40	$113.40
Purchase #6	$96.89	8.455%	$105.082	$105.08	$105.10	$105.10
Purchase #7	$232.52	11.329%	$258.8622	$258.86	$258.85	$258.90
7 purchase totals =	$978.49		$1,058.6611	$1,058.66	$1,058.65	$1,058.70