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	$147.27	3.307%	$152.1402	$152.14	$152.15	$152.10
Purchase #2	$40.63	6.291%	$43.186	$43.19	$43.20	$43.20
Purchase #3	$136.72	5.809%	$144.6621	$144.66	$144.65	$144.70
Purchase #4	$12.32	9.441%	$13.4831	$13.48	$13.50	$13.50
Purchase #5	$158.71	4.691%	$166.1551	$166.16	$166.15	$166.20
Purchase #6	$127.51	10.224%	$140.5466	$140.55	$140.55	$140.50
Purchase #7	$176.71	3.641%	$183.144	$183.14	$183.15	$183.10
7 purchase totals =	$799.87		$843.3171	$843.32	$843.35	$843.30