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	$42.25	12.842%	$47.6757	$47.68	$47.70	$47.70
Purchase #2	$111.68	3.459%	$115.543	$115.54	$115.55	$115.50
Purchase #3	$242.32	13.347%	$274.6625	$274.66	$274.65	$274.70
Purchase #4	$72.85	13.337%	$82.566	$82.57	$82.55	$82.60
Purchase #5	$184.35	6.523%	$196.3752	$196.38	$196.40	$196.40
Purchase #6	$193.95	12.771%	$218.7194	$218.72	$218.70	$218.70
Purchase #7	$151.71	8.319%	$164.3308	$164.33	$164.35	$164.30
7 purchase totals =	$999.11		$1,099.8726	$1,099.88	$1,099.90	$1,099.90