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	$94.86	9.648%	$104.0121	$104.01	$104.00	$104.00
Purchase #2	$67.81	6.643%	$72.3146	$72.31	$72.30	$72.30
Purchase #3	$24.86	4.253%	$25.9173	$25.92	$25.90	$25.90
Purchase #4	$105.31	10.636%	$116.5108	$116.51	$116.50	$116.50
Purchase #5	$13.87	3.373%	$14.3378	$14.34	$14.35	$14.30
Purchase #6	$204.41	3.294%	$211.1433	$211.14	$211.15	$211.10
Purchase #7	$39.30	5.728%	$41.5511	$41.55	$41.55	$41.60
7 purchase totals =	$550.42		$585.7870	$585.78	$585.75	$585.70