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	$131.78	6.762%	$140.691	$140.69	$140.70	$140.70
Purchase #2	$249.84	9.658%	$273.9695	$273.97	$273.95	$274.00
Purchase #3	$78.86	4.546%	$82.445	$82.45	$82.45	$82.40
Purchase #4	$77.82	9.335%	$85.0845	$85.08	$85.10	$85.10
Purchase #5	$210.28	7.326%	$225.6851	$225.69	$225.70	$225.70
Purchase #6	$32.79	6.196%	$34.8217	$34.82	$34.80	$34.80
Purchase #7	$174.81	11.173%	$194.3415	$194.34	$194.35	$194.30
7 purchase totals =	$956.18		$1,037.0383	$1,037.04	$1,037.05	$1,037.00