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	$44.92	10.314%	$49.553	$49.55	$49.55	$49.60
Purchase #2	$247.30	13.546%	$280.7993	$280.80	$280.80	$280.80
Purchase #3	$209.89	4.512%	$219.3602	$219.36	$219.35	$219.40
Purchase #4	$161.86	10.794%	$179.3312	$179.33	$179.35	$179.30
Purchase #5	$245.70	4.122%	$255.8278	$255.83	$255.85	$255.80
Purchase #6	$164.45	9.523%	$180.1106	$180.11	$180.10	$180.10
Purchase #7	$27.83	13.706%	$31.6444	$31.64	$31.65	$31.60
7 purchase totals =	$1,101.95		$1,196.6265	$1,196.62	$1,196.65	$1,196.60