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	$114.55	3.446%	$118.4974	$118.50	$118.50	$118.50
Purchase #2	$128.38	4.805%	$134.5487	$134.55	$134.55	$134.50
Purchase #3	$136.44	11.796%	$152.5345	$152.53	$152.55	$152.50
Purchase #4	$178.32	6.743%	$190.3441	$190.34	$190.35	$190.30
Purchase #5	$28.30	11.438%	$31.537	$31.54	$31.55	$31.50
Purchase #6	$167.36	6.635%	$178.4643	$178.46	$178.45	$178.50
Purchase #7	$102.44	7.186%	$109.8013	$109.80	$109.80	$109.80
7 purchase totals =	$855.79		$915.7273	$915.72	$915.75	$915.60