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	$59.74	12.707%	$67.3312	$67.33	$67.35	$67.30
Purchase #2	$78.93	4.789%	$82.71	$82.71	$82.70	$82.70
Purchase #3	$109.92	10.566%	$121.5341	$121.53	$121.55	$121.50
Purchase #4	$51.89	12.573%	$58.4141	$58.41	$58.40	$58.40
Purchase #5	$236.96	4.109%	$246.6967	$246.70	$246.70	$246.70
Purchase #6	$111.70	4.370%	$116.5813	$116.58	$116.60	$116.60
Purchase #7	$86.74	7.147%	$92.9393	$92.94	$92.95	$92.90
7 purchase totals =	$735.88		$786.2067	$786.20	$786.25	$786.10