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	$237.93	10.492%	$262.8936	$262.89	$262.90	$262.90
Purchase #2	$64.34	12.102%	$72.1264	$72.13	$72.15	$72.10
Purchase #3	$164.80	7.231%	$176.7167	$176.72	$176.70	$176.70
Purchase #4	$85.82	4.261%	$89.4768	$89.48	$89.50	$89.50
Purchase #5	$136.41	8.176%	$147.5629	$147.56	$147.55	$147.60
Purchase #6	$16.45	10.487%	$18.1751	$18.18	$18.20	$18.20
Purchase #7	$103.90	3.486%	$107.522	$107.52	$107.50	$107.50
7 purchase totals =	$809.65		$874.4735	$874.48	$874.50	$874.50