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	$235.76	11.242%	$262.2641	$262.26	$262.25	$262.30
Purchase #2	$50.42	9.871%	$55.397	$55.40	$55.40	$55.40
Purchase #3	$19.38	9.721%	$21.2639	$21.26	$21.25	$21.30
Purchase #4	$110.39	12.227%	$123.8874	$123.89	$123.90	$123.90
Purchase #5	$223.71	3.407%	$231.3318	$231.33	$231.35	$231.30
Purchase #6	$138.63	8.448%	$150.3415	$150.34	$150.35	$150.30
Purchase #7	$148.47	8.736%	$161.4403	$161.44	$161.45	$161.40
7 purchase totals =	$926.76		$1,005.9260	$1,005.92	$1,005.95	$1,005.90