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	$101.59	3.600%	$105.2472	$105.25	$105.25	$105.20
Purchase #2	$20.82	4.218%	$21.6982	$21.70	$21.70	$21.70
Purchase #3	$54.94	6.733%	$58.6391	$58.64	$58.65	$58.60
Purchase #4	$142.92	6.860%	$152.7243	$152.72	$152.70	$152.70
Purchase #5	$217.25	9.638%	$238.1886	$238.19	$238.20	$238.20
Purchase #6	$159.99	12.199%	$179.5072	$179.51	$179.50	$179.50
Purchase #7	$57.65	3.604%	$59.7277	$59.73	$59.75	$59.70
7 purchase totals =	$755.16		$815.7323	$815.74	$815.75	$815.60