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	$77.60	6.460%	$82.613	$82.61	$82.60	$82.60
Purchase #2	$225.93	10.478%	$249.6029	$249.60	$249.60	$249.60
Purchase #3	$250.97	7.419%	$269.5895	$269.59	$269.60	$269.60
Purchase #4	$194.93	12.703%	$219.692	$219.69	$219.70	$219.70
Purchase #5	$149.73	7.357%	$160.7456	$160.75	$160.75	$160.70
Purchase #6	$225.97	9.118%	$246.5739	$246.57	$246.55	$246.60
Purchase #7	$153.46	12.509%	$172.6563	$172.66	$172.65	$172.70
7 purchase totals =	$1,278.59		$1,401.4732	$1,401.47	$1,401.45	$1,401.50