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	$97.45	3.157%	$100.5265	$100.53	$100.55	$100.50
Purchase #2	$15.80	3.782%	$16.3976	$16.40	$16.40	$16.40
Purchase #3	$44.89	5.454%	$47.3383	$47.34	$47.35	$47.30
Purchase #4	$126.80	10.843%	$140.5489	$140.55	$140.55	$140.50
Purchase #5	$140.78	4.506%	$147.1235	$147.12	$147.10	$147.10
Purchase #6	$139.84	7.353%	$150.1224	$150.12	$150.10	$150.10
Purchase #7	$62.69	3.585%	$64.9374	$64.94	$64.95	$64.90
7 purchase totals =	$628.25		$666.9946	$667.00	$667.00	$666.80