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	$162.82	10.379%	$179.7191	$179.72	$179.70	$179.70
Purchase #2	$147.51	5.760%	$156.0066	$156.01	$156.00	$156.00
Purchase #3	$44.37	4.476%	$46.356	$46.36	$46.35	$46.40
Purchase #4	$215.44	3.259%	$222.4612	$222.46	$222.45	$222.50
Purchase #5	$50.95	3.299%	$52.6308	$52.63	$52.65	$52.60
Purchase #6	$186.42	11.860%	$208.5294	$208.53	$208.55	$208.50
Purchase #7	$111.73	4.119%	$116.3322	$116.33	$116.35	$116.30
7 purchase totals =	$919.24		$982.0353	$982.04	$982.05	$982.00