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	$61.44	6.581%	$65.4834	$65.48	$65.50	$65.50
Purchase #2	$81.98	11.647%	$91.5282	$91.53	$91.55	$91.50
Purchase #3	$132.32	10.270%	$145.9093	$145.91	$145.90	$145.90
Purchase #4	$203.86	7.624%	$219.4023	$219.40	$219.40	$219.40
Purchase #5	$126.85	10.737%	$140.4699	$140.47	$140.45	$140.50
Purchase #6	$114.67	11.134%	$127.4374	$127.44	$127.45	$127.40
Purchase #7	$238.54	12.148%	$267.5178	$267.52	$267.50	$267.50
7 purchase totals =	$959.66		$1,057.7483	$1,057.75	$1,057.75	$1,057.70