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	$174.51	12.854%	$196.9415	$196.94	$196.95	$196.90
Purchase #2	$156.35	5.294%	$164.6272	$164.63	$164.65	$164.60
Purchase #3	$105.67	11.705%	$118.0387	$118.04	$118.05	$118.00
Purchase #4	$74.67	10.504%	$82.5133	$82.51	$82.50	$82.50
Purchase #5	$227.93	12.270%	$255.897	$255.90	$255.90	$255.90
Purchase #6	$182.93	3.279%	$188.9283	$188.93	$188.95	$188.90
Purchase #7	$169.47	8.307%	$183.5479	$183.55	$183.55	$183.50
7 purchase totals =	$1,091.53		$1,190.4939	$1,190.50	$1,190.55	$1,190.30