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	$31.67	5.730%	$33.4847	$33.48	$33.50	$33.50
Purchase #2	$60.29	10.148%	$66.4082	$66.41	$66.40	$66.40
Purchase #3	$48.77	6.451%	$51.9162	$51.92	$51.90	$51.90
Purchase #4	$194.39	10.749%	$215.285	$215.29	$215.30	$215.30
Purchase #5	$81.93	9.554%	$89.7576	$89.76	$89.75	$89.80
Purchase #6	$54.72	10.137%	$60.267	$60.27	$60.25	$60.30
Purchase #7	$43.80	5.423%	$46.1753	$46.18	$46.20	$46.20
7 purchase totals =	$515.57		$563.2940	$563.31	$563.30	$563.40