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	$99.25	8.730%	$107.9145	$107.91	$107.90	$107.90
Purchase #2	$176.40	3.320%	$182.2565	$182.26	$182.25	$182.30
Purchase #3	$227.88	5.330%	$240.026	$240.03	$240.05	$240.00
Purchase #4	$43.56	8.504%	$47.2643	$47.26	$47.25	$47.30
Purchase #5	$187.82	5.624%	$198.383	$198.38	$198.40	$198.40
Purchase #6	$215.35	10.581%	$238.1362	$238.14	$238.15	$238.10
Purchase #7	$126.42	4.281%	$131.832	$131.83	$131.85	$131.80
7 purchase totals =	$1,076.68		$1,145.8125	$1,145.81	$1,145.85	$1,145.80