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	$167.58	11.559%	$186.9506	$186.95	$186.95	$187.00
Purchase #2	$74.65	5.589%	$78.8222	$78.82	$78.80	$78.80
Purchase #3	$27.69	6.566%	$29.5081	$29.51	$29.50	$29.50
Purchase #4	$131.35	11.839%	$146.9005	$146.90	$146.90	$146.90
Purchase #5	$142.39	10.715%	$157.6471	$157.65	$157.65	$157.60
Purchase #6	$164.51	12.864%	$185.6726	$185.67	$185.65	$185.70
Purchase #7	$153.53	7.373%	$164.8498	$164.85	$164.85	$164.80
7 purchase totals =	$861.70		$950.3509	$950.35	$950.30	$950.30