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	$12.73	13.638%	$14.4661	$14.47	$14.45	$14.50
Purchase #2	$117.80	10.815%	$130.5401	$130.54	$130.55	$130.50
Purchase #3	$128.40	12.526%	$144.4834	$144.48	$144.50	$144.50
Purchase #4	$52.95	4.711%	$55.4445	$55.44	$55.45	$55.40
Purchase #5	$181.46	8.190%	$196.3216	$196.32	$196.30	$196.30
Purchase #6	$96.56	8.271%	$104.5465	$104.55	$104.55	$104.50
Purchase #7	$130.38	9.408%	$142.6462	$142.65	$142.65	$142.60
7 purchase totals =	$720.28		$788.4484	$788.45	$788.45	$788.30