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	$104.64	12.361%	$117.5746	$117.57	$117.55	$117.60
Purchase #2	$218.56	4.641%	$228.7034	$228.70	$228.70	$228.70
Purchase #3	$82.57	6.161%	$87.6571	$87.66	$87.65	$87.70
Purchase #4	$89.78	7.727%	$96.7173	$96.72	$96.70	$96.70
Purchase #5	$132.88	7.269%	$142.539	$142.54	$142.55	$142.50
Purchase #6	$71.33	10.382%	$78.7355	$78.74	$78.75	$78.70
Purchase #7	$29.85	7.118%	$31.9747	$31.97	$31.95	$32.00
7 purchase totals =	$729.61		$783.9016	$783.90	$783.85	$783.90