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	$139.88	11.263%	$155.6347	$155.63	$155.65	$155.60
Purchase #2	$198.59	13.409%	$225.2189	$225.22	$225.20	$225.20
Purchase #3	$50.68	11.613%	$56.5655	$56.57	$56.55	$56.60
Purchase #4	$41.73	6.536%	$44.4575	$44.46	$44.45	$44.50
Purchase #5	$152.43	4.320%	$159.015	$159.02	$159.00	$159.00
Purchase #6	$168.74	11.431%	$188.0287	$188.03	$188.05	$188.00
Purchase #7	$233.83	8.870%	$254.5707	$254.57	$254.55	$254.60
7 purchase totals =	$985.88		$1,083.4910	$1,083.50	$1,083.45	$1,083.50