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	$154.92	8.848%	$168.6273	$168.63	$168.65	$168.60
Purchase #2	$185.70	3.291%	$191.8114	$191.81	$191.80	$191.80
Purchase #3	$152.55	4.849%	$159.9471	$159.95	$159.95	$159.90
Purchase #4	$99.57	13.234%	$112.7471	$112.75	$112.75	$112.70
Purchase #5	$152.71	10.347%	$168.5109	$168.51	$168.50	$168.50
Purchase #6	$29.47	12.429%	$33.1328	$33.13	$33.15	$33.10
Purchase #7	$219.28	13.356%	$248.567	$248.57	$248.55	$248.60
7 purchase totals =	$994.20		$1,083.3436	$1,083.35	$1,083.35	$1,083.20