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	$189.48	11.424%	$211.1262	$211.13	$211.15	$211.10
Purchase #2	$73.84	6.139%	$78.373	$78.37	$78.35	$78.40
Purchase #3	$239.43	11.520%	$267.0123	$267.01	$267.00	$267.00
Purchase #4	$10.83	9.519%	$11.8609	$11.86	$11.85	$11.90
Purchase #5	$86.86	3.623%	$90.0069	$90.01	$90.00	$90.00
Purchase #6	$81.61	10.206%	$89.9391	$89.94	$89.95	$89.90
Purchase #7	$186.58	12.680%	$210.2383	$210.24	$210.25	$210.20
7 purchase totals =	$868.63		$958.5567	$958.56	$958.55	$958.50