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	$184.80	6.260%	$196.3685	$196.37	$196.35	$196.40
Purchase #2	$184.39	6.832%	$196.9875	$196.99	$197.00	$197.00
Purchase #3	$186.42	5.600%	$196.8595	$196.86	$196.85	$196.90
Purchase #4	$20.55	6.318%	$21.8483	$21.85	$21.85	$21.80
Purchase #5	$201.27	13.677%	$228.7977	$228.80	$228.80	$228.80
Purchase #6	$103.96	4.805%	$108.9553	$108.96	$108.95	$109.00
Purchase #7	$108.66	6.158%	$115.3513	$115.35	$115.35	$115.40
7 purchase totals =	$990.05		$1,065.1681	$1,065.18	$1,065.15	$1,065.30