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	$208.89	10.752%	$231.3499	$231.35	$231.35	$231.30
Purchase #2	$186.71	5.716%	$197.3823	$197.38	$197.40	$197.40
Purchase #3	$51.27	7.233%	$54.9784	$54.98	$55.00	$55.00
Purchase #4	$245.78	7.601%	$264.4617	$264.46	$264.45	$264.50
Purchase #5	$88.38	6.736%	$94.3333	$94.33	$94.35	$94.30
Purchase #6	$131.39	4.709%	$137.5772	$137.58	$137.60	$137.60
Purchase #7	$103.73	5.658%	$109.599	$109.60	$109.60	$109.60
7 purchase totals =	$1,016.15		$1,089.6818	$1,089.68	$1,089.75	$1,089.70