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	$29.44	10.407%	$32.5038	$32.50	$32.50	$32.50
Purchase #2	$205.79	13.403%	$233.372	$233.37	$233.35	$233.40
Purchase #3	$88.90	11.349%	$98.9893	$98.99	$99.00	$99.00
Purchase #4	$165.69	13.766%	$188.4989	$188.50	$188.50	$188.50
Purchase #5	$202.32	6.577%	$215.6266	$215.63	$215.65	$215.60
Purchase #6	$38.46	13.725%	$43.7386	$43.74	$43.75	$43.70
Purchase #7	$149.81	9.813%	$164.5109	$164.51	$164.50	$164.50
7 purchase totals =	$880.41		$977.2401	$977.24	$977.25	$977.20