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	$38.72	13.272%	$43.8589	$43.86	$43.85	$43.90
Purchase #2	$170.46	12.157%	$191.1828	$191.18	$191.20	$191.20
Purchase #3	$207.70	4.728%	$217.5201	$217.52	$217.50	$217.50
Purchase #4	$175.47	9.371%	$191.9133	$191.91	$191.90	$191.90
Purchase #5	$232.46	10.409%	$256.6568	$256.66	$256.65	$256.70
Purchase #6	$18.41	5.203%	$19.3679	$19.37	$19.35	$19.40
Purchase #7	$31.35	3.719%	$32.5159	$32.52	$32.50	$32.50
7 purchase totals =	$874.57		$953.0157	$953.02	$952.95	$953.10