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	$150.55	8.190%	$162.88	$162.88	$162.90	$162.90
Purchase #2	$147.61	13.321%	$167.2731	$167.27	$167.25	$167.30
Purchase #3	$186.84	13.102%	$211.3198	$211.32	$211.30	$211.30
Purchase #4	$133.73	6.209%	$142.0333	$142.03	$142.05	$142.00
Purchase #5	$241.78	6.110%	$256.5528	$256.55	$256.55	$256.60
Purchase #6	$84.61	6.820%	$90.3804	$90.38	$90.40	$90.40
Purchase #7	$152.25	8.284%	$164.8624	$164.86	$164.85	$164.90
7 purchase totals =	$1,097.37		$1,195.3018	$1,195.29	$1,195.30	$1,195.40