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	$164.75	9.109%	$179.7571	$179.76	$179.75	$179.80
Purchase #2	$236.81	11.514%	$264.0763	$264.08	$264.10	$264.10
Purchase #3	$215.30	10.781%	$238.5115	$238.51	$238.50	$238.50
Purchase #4	$104.52	11.487%	$116.5262	$116.53	$116.55	$116.50
Purchase #5	$56.43	8.864%	$61.432	$61.43	$61.45	$61.40
Purchase #6	$173.45	7.653%	$186.7241	$186.72	$186.70	$186.70
Purchase #7	$36.69	4.776%	$38.4423	$38.44	$38.45	$38.40
7 purchase totals =	$987.95		$1,085.4695	$1,085.47	$1,085.50	$1,085.40