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	$152.78	3.111%	$157.533	$157.53	$157.55	$157.50
Purchase #2	$86.50	3.798%	$89.7853	$89.79	$89.80	$89.80
Purchase #3	$191.90	4.873%	$201.2513	$201.25	$201.25	$201.30
Purchase #4	$40.95	5.684%	$43.2776	$43.28	$43.30	$43.30
Purchase #5	$9.94	9.607%	$10.8949	$10.89	$10.90	$10.90
Purchase #6	$215.66	10.659%	$238.6472	$238.65	$238.65	$238.60
Purchase #7	$90.68	5.109%	$95.3128	$95.31	$95.30	$95.30
7 purchase totals =	$788.41		$836.7021	$836.70	$836.75	$836.70