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	$246.64	3.197%	$254.5251	$254.53	$254.55	$254.50
Purchase #2	$55.46	13.330%	$62.8528	$62.85	$62.85	$62.90
Purchase #3	$168.30	4.867%	$176.4912	$176.49	$176.50	$176.50
Purchase #4	$43.65	5.171%	$45.9071	$45.91	$45.90	$45.90
Purchase #5	$96.28	4.479%	$100.5924	$100.59	$100.60	$100.60
Purchase #6	$209.58	5.454%	$221.0105	$221.01	$221.00	$221.00
Purchase #7	$184.98	10.210%	$203.8665	$203.87	$203.85	$203.90
7 purchase totals =	$1,004.89		$1,065.2456	$1,065.25	$1,065.25	$1,065.30