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	$238.30	7.691%	$256.6277	$256.63	$256.65	$256.60
Purchase #2	$127.86	3.167%	$131.9093	$131.91	$131.90	$131.90
Purchase #3	$65.68	10.460%	$72.5501	$72.55	$72.55	$72.60
Purchase #4	$202.31	5.567%	$213.5726	$213.57	$213.55	$213.60
Purchase #5	$114.93	9.510%	$125.8598	$125.86	$125.85	$125.90
Purchase #6	$99.64	7.693%	$107.3053	$107.31	$107.30	$107.30
Purchase #7	$166.89	4.236%	$173.9595	$173.96	$173.95	$174.00
7 purchase totals =	$1,015.61		$1,081.7843	$1,081.79	$1,081.75	$1,081.90