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	$190.42	12.291%	$213.8245	$213.82	$213.80	$213.80
Purchase #2	$157.28	7.295%	$168.7536	$168.75	$168.75	$168.80
Purchase #3	$21.31	9.479%	$23.33	$23.33	$23.35	$23.30
Purchase #4	$109.75	5.563%	$115.8554	$115.86	$115.85	$115.90
Purchase #5	$181.62	8.322%	$196.7344	$196.73	$196.75	$196.70
Purchase #6	$246.55	8.515%	$267.5437	$267.54	$267.55	$267.50
Purchase #7	$151.96	3.245%	$156.8911	$156.89	$156.90	$156.90
7 purchase totals =	$1,058.89		$1,142.9327	$1,142.92	$1,142.95	$1,142.90