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	$231.65	5.386%	$244.1267	$244.13	$244.15	$244.10
Purchase #2	$81.70	4.712%	$85.5497	$85.55	$85.55	$85.50
Purchase #3	$84.67	7.391%	$90.928	$90.93	$90.95	$90.90
Purchase #4	$77.74	10.509%	$85.9097	$85.91	$85.90	$85.90
Purchase #5	$202.38	3.637%	$209.7406	$209.74	$209.75	$209.70
Purchase #6	$30.64	9.171%	$33.45	$33.45	$33.45	$33.50
Purchase #7	$35.81	4.681%	$37.4863	$37.49	$37.50	$37.50
7 purchase totals =	$744.59		$787.1910	$787.20	$787.25	$787.10