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	$41.97	5.514%	$44.2842	$44.28	$44.30	$44.30
Purchase #2	$89.86	10.746%	$99.5164	$99.52	$99.50	$99.50
Purchase #3	$230.73	8.163%	$249.5645	$249.56	$249.55	$249.60
Purchase #4	$198.57	9.753%	$217.9365	$217.94	$217.95	$217.90
Purchase #5	$189.88	9.710%	$208.3173	$208.32	$208.30	$208.30
Purchase #6	$142.56	3.642%	$147.752	$147.75	$147.75	$147.80
Purchase #7	$76.68	7.686%	$82.5736	$82.57	$82.55	$82.60
7 purchase totals =	$970.25		$1,049.9445	$1,049.94	$1,049.90	$1,050.00