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	$164.96	13.526%	$187.2725	$187.27	$187.25	$187.30
Purchase #2	$191.70	8.478%	$207.9523	$207.95	$207.95	$208.00
Purchase #3	$194.45	5.682%	$205.4986	$205.50	$205.50	$205.50
Purchase #4	$81.57	12.616%	$91.8609	$91.86	$91.85	$91.90
Purchase #5	$85.79	8.271%	$92.8857	$92.89	$92.90	$92.90
Purchase #6	$93.73	7.427%	$100.6913	$100.69	$100.70	$100.70
Purchase #7	$82.91	8.360%	$89.8413	$89.84	$89.85	$89.80
7 purchase totals =	$895.11		$976.0026	$976.00	$976.00	$976.10