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	$5.38	10.540%	$5.9471	$5.95	$5.95	$5.90
Purchase #2	$104.83	12.607%	$118.0459	$118.05	$118.05	$118.00
Purchase #3	$15.38	3.267%	$15.8825	$15.88	$15.90	$15.90
Purchase #4	$112.30	9.764%	$123.265	$123.27	$123.25	$123.30
Purchase #5	$189.38	5.771%	$200.3091	$200.31	$200.30	$200.30
Purchase #6	$179.46	4.460%	$187.4639	$187.46	$187.45	$187.50
Purchase #7	$231.74	13.411%	$262.8187	$262.82	$262.80	$262.80
7 purchase totals =	$838.47		$913.7322	$913.74	$913.70	$913.70